Bigger Little Brother

by Megapone

Rating: mature
Tags: Slice of Life, Alternate Universe
Length: 18817

Shining Armor has always known that his brother Dusk is smarter than him, and shorter than him. But one day, he finds Dusk standing eye-to-eye with him—and his "little" brother's growth spurt doesn't look set to stop there.

There have always been two constants in Shining Armor's life: (1) His brother Dusk is smarter than him, and (2) His brother Dusk is shorter than him. But one day, he finds Dusk standing eye-to-eye with him—and his "little" brother's growth spurt doesn't look set to stop there.

As Dusk grows bigger and bigger by the day, Shining Armor struggles to adapt to being the "little" sibling. Meanwhile, Dusk struggles with new, growing urges, not all of them innocent. Just how big will Dusk Shine get? And will his new size awake new feelings—and new lusts—in both "bigger" and "smaller" siblings alike?

Coverart by Cosmonaut.

Published 1970-01-01 00:00:00 UTC
Last updated 2015-10-27 21:49:35 UTC

Chapter One: Not-So-Little Brother

Something was different about Dusk Shine.

Was it the manestyle? No. It was about as messy as ever, except for the spots where Mom had attacked it with a pair of scissors last week. Was he wearing something new? Was he not wearing something that he normally did?

Nope. Dusk was wearing around the same thing he always did—which was to say, nothing at all. Pretty standard pony fare, then.

Huh.

Shining Armor frowned, watching his brother trot up to Mom and give her a hug. There was definitely something...off about him.

“Morning, BBBFF.” Dusk trotted up to the table, his mane bouncing around his ears. He had that dorky little grin on his face, the one that he always had when he found the answer to one of his homework problems.

Huh. His voice sounded a little different—lower, maybe. Then again, Dusk was still just fifteen. Still coming out of puberty, so that might make sense. Could that be all? He still felt a bit uneasy, but was more than willing to write the whole thing off as a case of pre-coffee weirdness. He knew he should’ve never let Dad get him hooked on the stuff.

Shining grinned back and nodded to his brother. “Morning to you too, Dusk. How’s it going?”

“Pretty well. I woke up feeling great this morning.”

“Oh, Shiny? Could you come help me with these dishes?”

“Sure, Mom.” Shining and Dusk exchanged a look. Both stallions rolled their eyes. Then, Shining slipped out of his chair, his hooves clip-clopping against the tiled floor. It was only then that he realized what was different about Dusk.

There were two constants in Shining Armor’s life. One: Dusk Shine was smarter than him; and two: Dusk Shine was shorter than him. Sure, Dusk might have helped him out in some of his harder math classes, but Shining had always been there to protect him whenever an overzealous classmate decided to pick on the “easy target.”

Sure, Dusk probably knew enough spells to protect himself if need be, but Shining had always viewed shields as more than just his particular branch of magic. He was his little brother’s shield—his protector, his watcher, his inspiration. He’d always been, and always would be, the bigger brother.

Until today.

Shining blinked. Usually, the top of Dusk’s head just about came up to his muzzle. Today, though, he found himself meeting Dusk’s gaze eye-to-eye. On pure reflex, he glanced down—was Dusk standing on something? Was he bowing his legs? But no; it looked like Dusk was just about as tall as he was. Their hooves were even the same size. Shining had always had big hooves—and had been somewhat proud of them, even, given how Cadance loved to tease him about “stallions with big hooves”—but now it looked like Dusk’s had grown to match.

How had this happened? Shining kept staring at Dusk’s chest. He searched his memory, trying to find whether Dusk had been getting any taller lately. But no—he’d just told him good night yesterday, and he’d been the same height he’d always been. But not this morning.

How?

“Shiny!” Mom sounded a little bit annoyed. “Come on! I’ve got to finish these up so I can get to work!”

“Coming, Mom!”

As Shining turned to go, Dusk caught him on the shoulder. “Hey, Shining?” he asked. His voice might have been a bit deeper, but it contained the same dorky inflection that Dusk had always had. He was eyeing Shining’s plate of food hungrily—Shining had only had time to finish half of it, and there was still a bit of omelette, and two pieces of toast there. “You gonna finish that? I’m feeling really hungry today.”

“Uh.” Shining’s eyes flickered back to Mom, who was glaring at him from the sink. “Sure. Whatever.”

“Thanks!” Dusk beamed at him. Shining just smirked, though somewhat awkwardly, and trotted over to the sink.

“Hey, Mom?” He turned to her as he started to lift the first stack of dishes. “Does Dusk look a little bit...bigger to you, today?”

“Oh, you noticed too?” Instantly, all traces of irritation had vanished from her voice. Her face lit up, and there was a bounce in her voice as she continued. “Little Dusk’s finally having his growth spurt—why, he looks down on me now! Goodness knows he’s had to wait long enough.”

“Heh.” Shining nodded. That must be it. Just a normal growth spurt. “Definitely.”

“Oh, it’s just so wonderful. Now I’ve got three big, strong stallions in the family!”

Wonderful. Right. As Shining Armor started to wipe off the plates, he turned his mother’s words over in his head. Growth spurt. Sure.

But whose were definitely not supposed to happen overnight—at least, not by much. Then again, Dusk had always been a little bit weird. Take a colt with awesome magical power, pair him up with an alicorn princess, and you’d always have a recipe for a bit of an odd life. Maybe it was just “a Dusk thing.”

Still…

He looks down on me, now, Mom had said. A shiver went down Shining’s spine. If Dusk got any bigger…

But no. That couldn’t happen. He might not be the bigger brother anymore, but he was still the older one. Dusk had to be done growing. This was just a fluke. And besides, Shining decided, maybe he’d grow to prefer looking his brother in the eye.

It was around lunchtime that Shining decided that he’d definitely preferred looking down at Dusk.

It wasn’t just that he’d passed Dusk two or three times in the halls now, and had had to jerk his gaze up by a few inches when he realized he’d been staring right at Dusk’s chest. It wasn’t just that Dusk seemed bigger in a way that was more than just physical—he now stood a little bit straighter, a little bit taller, with the barest hint of a smirk playing across his face. He hadn’t even been sure that Dusk could smirk.

The problem was his friends—or, as Shining was now mentally calling them, his former friends.

“Wowzers.” Poindexter blinked past Shining’s shoulder. “You sure that’s your brother, Shining?”

Shining groaned as Poindexter leaned over to take a sip from one of the school cafeteria’s crappy milk cartons. “Yes,” he said, only a little bitterly. “I’ve only told you three times already.”

“Dude, c’mon.” 8-bit leaned back on the back legs of his chair. “Colts don’t just grow, like, four or five inches overnight. You sure he didn’t mess up some kind of magic spell or something?”

“Maybe he’s been growing,” Gaffer said. He twirled a pencil beside his head, his magic flickering around it. “Maybe we just didn’t notice.”

“Dude, we just went to Shiny’s house last weekend,” 8-bit said. “We saw Dusk.”

“For about five seconds. And then he ducked into his room to study, like he always does. Did you tape-measure him or something while you were there?”

8-bit actually had the gall to look thoughtful about that. “Y’know,” he said, scratching his muzzle, “I do wonder how much he’s actually grown.”

“Can we stop talking about how tall my little brother is?” Shining cut in. “Seriously. Guys. I don’t even understand why you care.”

8-bit grinned at him. It was absolutely insufferable. “Why’s that, Shiny? Especially ‘cuz it sounds like you care quite a lot.”

“Shiny?” Shining said. “You trying to be Cadance now?”

“Well,” 8-bit said. “Maybe she’ll go for the bigger stallion, if y’know what I mean.”

Shining actually lunged at him. Gaffer held him back, but 8-bit was laughing too hard to care. “Just messin’ with you, dude,” he said. “Don’t take it seriously.”

“Don’t take what seriously?”

“Cadance!” Shining and Gaffer straightened up real quick. He whirled and put on his best innocent grin. “How’s it going?”

“Pretty well.” Cadance smiled up at him. “What’re you guys talking about?”

Before Shining could say “nothing,” Poindexter blurted, “His brother.”

“His—oh, Dusk?” Cadance blinked up at Shining. “I did notice he looked a bit taller today.”

“Heh. Yeah.” Shining scratched the back of his head and quashed the urge to throttle Poindexter. “Uh, Mom just says he’s getting his growth spurt.”

“Neat,” Cadance said. “And has he been using the weight room? Looks like he’s looking to follow in your hoofsteps.”

Shining glanced down at his chest reflexively. He’d been using the school gym somewhat regularly ever since he’d decided at the end of last year that he wanted to join the Royal Guard, and had filled out a good amount, at least compared to how reedy he'd been before. He glanced back over to Dusk. Sure enough, Dusk wasn’t just taller than yesterday. He was thicker, too—he hadn’t grown like a weed; he’d filled out. His foreleg was even just a little bit less brawny than Shining’s.

“Sorry?” Shining said. He did so through gritted teeth.

“Well, it looks like he wants to join the Guard too.” Cadance chuckled and poked his chest with a hoof. “Either that, or he wants to join the hoofball team once Buck graduates. You didn’t tell me he’d been working out.”

“He...hasn’t.” Shining swallowed. His mouth suddenly felt very dry.

“Huh. Weird.” Before he could react, Cadance sprang forward and planted a kiss on his cheek. When she pulled back, the smile on her face could have lit up any dark room. “I’ll see you at Frozen Treats after school?”

“Oh—yeah!” Shining grinned at her. It was only a little forced. “Sure. I’ll meet you in the courtyard?”

“You got it, general.” Cadance snapped off a quick salute, then burst out giggling. As she turned to go, she gave him a quick wave, then disappeared into the crowd.

Shining watched her go. Then:

“So,” 8-bit said. “Shining. What do you think—”

“Not another word,” Shining bit out. 8-bit wisely shut up.

The next day, Shining realized that Dusk was taller than him.

It wasn’t some kind of huge moment of revelation. It wasn’t even obvious—there was no moment when Dusk walked up to him, smirked, and said, “Hah! You’re short.”

Instead, when they were walking home from school, Shining merely noticed that anytime he turned to talk to Dusk, he was looking up, not across.

“—and can you believe it? Professor Neigh actually thought that the answer was two pi. Well, I actually checked the textbook, and according to chapter three—”

“Hey, Dusk?”

Dusk stopped blinking. They kept walking, though. Shining had to move a little bit faster to keep up; Dusk wasn’t that much taller than him now, but his strides were still a bit longer, a bit easier than his.

“What’s up, Shining?” Dusk glanced over—down—at him, blinking innocently. His tousled mane fell over his forehead like the eternal mop that it was, except now Shining wasn’t able to see the top. He could actually see the underside of Dusk’s horn, now, and it looked a good half-inch longer than his own.

Shining took a moment to consider his next words. “Are you...feeling okay? Like, not sick or anything?”

Dusk gave him a funny look. His heavier footfalls padded noticeably on the Canterlot street, clop-clopping at a slightly louder volume than Shining’s. “Sick? Why would I be sick? Have I been sweating a lot or something?”

“No, no.” Though, Shining privately noted, Dusk’s scent had been a lot stronger than usual. Shaking that thought off—why was he noticing how his brother smelled, of all ponies?—he continued with, “I just thought—well, you’ve been going through a lot of changes lately, and I wanted to make sure that you weren’t, y’know, in pain or anything.”

Dusk digested that for a moment. “Pain?” he finally asked. “Why would I be in pain? I feel great.”

“Sure, sure,” Shining said quickly. He’d misstepped. The curiosity in Dusk’s voice was something he really didn’t want to address right now. “Forget I even asked.”

Dusk was frowning. “You’re talking about this growth spurt, right? Why would that be a bad thing? Mom said that it’s normal for a stallion my age.”

“Yes,” Shining said, “technically. But—I mean, five inches in three days? That’s not exactly healthy, is it?”

“Why not?” Dusk stood up a little straighter. With a start, Shining noticed that his “little” brother’s chest actually puffed up a little bigger, a little wider than his own. “I told you, it feels great. Being bigger feels great.”

A shiver went down Shining’s spine. “Like I said,” he said. “Forget I asked.”

“I don’t know, B.B.B.F.F.” Dusk stopped abruptly; Shining jerked to a stop a foot or two ahead of him. “Or should I say, L.B.B.F.F.?”

Shining’s spine tingled again. “Uh. Sorry?”

Dusk was grinning. He wasn’t smirking—Dusk didn’t smirk; he was too nice for that—but the grin on his muzzle stretched from ear to ear. “Little brother, best friend forever.”

Shining almost choked. “I don’t think you can change that so easily.”

“Maybe not,” Dusk said. He shrugged. “But if growing is so easy...why not?” He shot Shining another grin. This one was mutual—Shining felt like he could smile back this time, albeit a bit awkwardly.

Dusk abruptly punched Shining in the shoulder. It was a friendly motion, one that they’d shared a thousand times. But with Dusk’s new strength, Shining actually felt himself wince at the force of Dusk’s hoof. Dusk didn’t seem to notice. “Want to race home?” he asked.

“We haven’t done that in years,” Shining said.

“So?” Dusk rolled his neck; Shining winced again when he heard his brother’s joints popping. “It’ll be more fun than walking.”

“I...guess?” Shining glanced up at Dusk and saw something new behind his brother’s eyes. He wasn’t sure what it was, but it sent his stomach fluttering like a butterfly.

“Great! On your marks”—Dusk leaned forward, angling his body straight down the street—”get set, go!”

Shining barely managed to get off in time. Dusk was laughing all the way, and even Shining was able to smile by the halfway point, though he was breathing hard.

Shining had always won their races, for as far back as he could remember. Thankfully, he won this one too—though Dusk was just a second or two behind him. Shining was breathing hard; he couldn’t remember the last time he’d run that fast. Meanwhile, Dusk looked barely winded.

At least, Shining assured himself as he unlocked the front door, Dusk chattering eagerly behind him, his brother wasn’t likely to get any bigger. Shining himself was already on the tall end for a stallion, and Dusk was just an inch or so above that. Freakish sudden growth spurts or not, he’d more likely than not taper off here. Shining decided he could live with that.

And yet...somehow, Shining felt that when Dusk followed him inside, he had to look a little bit further up to meet his brother’s eyes. Crane his neck a little bit further back.

But it’d only been a few minutes. He couldn’t have grown bigger in that time—it was impossible. Should be impossible.

Wasn’t it?

By the end of the week, Shining had to revise his initial hypothesis.

It wasn’t, as it turned out, impossible for Dusk to keep growing. If anything, it was exactly the opposite.

If he’d shot up like a weed over the first forty-eight hours, Dusk's growth spurt seemed set on outdoing itself over the next few days. Each morning, Shining found himself having to crane his neck back a bit more to meet Dusk’s eyes; each night, he found Dusk looking down a little bit further on him, having grown even more throughout the day.

By the end of the second day of his growth spurt, Dusk had been an estimated two inches taller than Shining. By the end of the third day, he was four inches taller. By the fourth day, he was a half-foot taller—within twenty-four hours of that, he’d shot up another five inches, making his full growth spurt come out to an incredible fifteen inches of height! And by the looks of it, he was nowhere near done.

Shining had always thought of himself as a tall stallion. Coming out to around 5’11” at the bottom of his horn, he’d always been taller than almost all of his classmates. The average size for a unicorn stallion was 5’6”—slightly taller than a pegasus’ 5’5”, and a good bit shorter than the average earth pony’s 5’9”. Being in the top-tier, heightwise, had propelled Shining through most of adolescence, even if he had been a bit awkward and lanky for the first few years.

Once he’d decided to sign up for the Guard, though, his workout sessions had paid off. He’d filled out, his chest widening and his forelegs thickening a good bit. Even Cadance had made a few lewd remarks on the improvement of his flank. Once he’d gotten through blushing and stammering in response, Shining had been forced to admit that she was right. He was a bigger stallion than he’d been: stronger, more confident. And when he’d started out as a big stallion in the first place, every improvement just let him puff out his chest a little bit more. Take that Buck, he’d thought to himself more than once, thinking of his former bully with no small amount of relish.

But Dusk made all that look insignificant. Princess Celestia was the tallest pony in the land—on top of a whole pile of other alicorn benefits—and even she “only” stood at a height of 6’5”. Dusk had reached that size that on his fourth day of growing, and had passed her after a single night’s sleep! Shining’s brother was actually taller—bigger—than the Princess! An alicorn! His teacher!

And that wasn’t the only place he’d been growing. Every day, Dusk’s breaths seemed to fill his chest a little bit more; every morning, his legs and haunches were a little thicker, his whole body seeming to revel in its new and impending size. And with so much size to feed, it needed a lot of fuel. Picking over Shining’s leftovers had stopped being worthwhile on Dusk’s third day of growth—by the fourth morning, he was complaining of hunger even after Mom had cooked him two breakfasts. By the fifth, it seemed that Dusk’s daily caloric intake was high enough to clear out the fridge every day. If not for his royal student’s stipend and Mom and Dad’s tenure, Shining might have been worried that Dusk’s stomach would empty the entire family’s wallets.

Dusk was almost seven feet tall. Absolutely nopony even came close to him now. Even the tallest earth pony stallion at the Academy, an exchange student from Fillydelphia, only came up to his shoulder! It was insane!

Shining had quickly been forced to deal with the new reality: His brother was bigger than him—no; huger than him—and was only going to get more so. Yet he couldn’t quell the quiver of inadequacy in his gut, the shiver going down his spine as he saw Dusk reach new, greater heights each day, overturning years of a physically enforced status quo. For all his life, Shining had been the bigger brother. And now, he...wasn’t.

Now, when Dusk passed him in the hallway, or when the two of them were walking home from school—the market—anywhere—everyone’s eyes went to Dusk first, and Shining second, if at all. Shining had been proud when Dusk had been accepted as Princess Celestia’s personal student. He hadn’t minded one bit when ponies had started to ask him about his “genius brother.” He’d been overjoyed—the proudest big brother in the world.

But now, Dusk was all but larger than life. Shining couldn’t help but feel small next to him, and in more ways than just one. Everything about Dusk was big: His brain, his appetite, his strength—even his magic. More than one time, Shining would come down to the kitchen to find the whole room fizzling with magical potential energy, and Dusk sitting down (or standing, now that he was too big to sit in most of their chairs), eating, having just used a simple levitation spell to make himself a sandwich out of everything he’d managed to scrounge out of the vegetable drawer. There was just too much of him—too much power, too much strength, too much size.

And too much volume, too. Shining blushed to remember it. He knew, intellectually, that Dusk was a male adolescent. He also knew what kind of urges tended to come along with that time of life—goodness knew that he’d dealt with them enough of them himself, and had only started to “enjoy” them with Cadance whenever her roommate was out of the house. He and Dusk had even talked about healthy habits and good sources of, ah, inspiration more than once.

But the moment Shining Armor had walked past Dusk’s closed bedroom the previous night, he’d known that something had fundamentally changed. He could hear Dusk’s grunts, the steady thump-thump of what could only be hips smacking against a mattress, echoing past the doorframe. They weren’t even that loud, not intentionally. They were just big—just like him.

Blushing madly, Shining had managed to pull himself away and back to his own room (where he may or may not have found himself engaged in a similar activity an hour or so later), but he found his mind stuck on the scene he’d overheard, like a broken record. Dusk’s grunts had been more sensual, more involved than anything Shining had ever felt. The slaps of his body against the mattress had been louder than anything Shining could make intentionally, and he had little doubt that, given enough time, Dusk’s thrusts would be shaking more than just his own mattress.

Shining had gotten up sometime around two in the morning, drowsy, grumpy, and thirsty as hell. After relieving himself and levitating a glass of water upstairs, he’d trekked back down the hall to his bedroom—only to hear the same sounds coming out of Dusk’s room again. It’d been five hours—there was no way he was still going. And yet Shining could still hear him, loud and clear: his grunts and thumps, if anything, sounded even louder, even heavier, than when they had earlier. And when the last thump had finally sounded, Dusk’s ensuing moan had gone on for a good thirty seconds. Thirty seconds!

The moment his own door closed behind him, Shining realized that he was panting. At first glance, he thought it was obvious why—he’d just eavesdropped on his younger brother in the middle of what was obviously a very, ah, personal activity. But that wasn’t the real reason. The second he flopped back into bed, he found a very long, very stiff friend of his poking up over his belly and throbbing expectantly.

Shining wasn’t just tall in one place—even Cadance had commented on his size at one point ,rather gleefully. But as he bit his lip and got to work—there was absolutely no ignoring it; even though he’d gotten off earlier, he had a feeling that he wouldn’t be able to sleep otherwise—he felt a sinking curiosity about Dusk’s true—or, rather, new—size. The rest of him was huge. How big would he be...down there?

Shining had to bite down harder to stop himself from moaning aloud. As it was, his arousal came out as a very muffled, very turned-on grunt, that thankfully—he hoped—didn’t penetrate the walls. The whole time, seemingly against his will, he found his mind dominated by thoughts of Dusk: of how big he was, of how big he was getting, and how big he might eventually be. The thought of how much that bed had been shaking, of just how long that moan had been, soon sent him over the edge.

Tired, sticky, and more than a little bit sore, Shining had little trouble finally falling back asleep. This time, though, he found his waking thoughts soon turning into dreams. Where his dreams earlier had been about Cadance and a game of Ogres and Oubliettes, his new dreams drifted through visions of his “little” brother: Dusk, big, and getting bigger.

They were good dreams.

Chapter Two: Growing Pains

The next morning, when Shining passed Dusk’s room on his way to the bathroom, he couldn’t help but linger for a moment. Unlike last night, it was absolutely quiet—there wasn’t a sound to be heard. Shining’s ears pricked up, though, when they detected something after all—a low, steady rumbling. Snoring?

He should turn back around, keep heading to the bathroom. But all the same...he needed to see this. He’d see Dusk at breakfast, or throughout the day, but here, in his room, it somehow felt...different. Dusk must be asleep—why else would he be snoring? Shining could just snag a quick glance and then be on his way.

He didn’t know why, really, why he felt like this—why he suddenly needed to look at his brother like this. It was just a whim, an urge that grew inside of him until it was all he could do to stop himself from bucking open the door right then and there. Swallowing the lump in his throat, Shining summoned up his magic, then silently twisted the door handle open.

The door whispered silently over the carpet inside. Shining, moving as slowly and quietly as he could manage, peeked his eye through the crack in the door.

The first thing he noticed was the scent—the musk, that is. Dusk’s scent permeated every pore of his nose, filling his lungs with each breath he took. It was almost stifling: strong, masculine, overpowering. It was a big smell, and, as Shining pushed the door open a little bit further, it more than matched its owner.

Dusk was lying on his bed, splayed across it with his hooves flung out around him. Even though his horn was poking against the headboard, his hindlegs went over the bottom of the mattress, his forelegs dangling over the sides. He was easily too big for his bed—bought for a much smaller colt, it was far too small for this almost cartoonishly big stallion. Shining blinked, swallowing, as he watched the steady rise and fall of Dusk’s wide chest.

That wasn’t the only thing that was rising and falling, though. Shining’s eyes widened, his breath catching in his chest when he caught sight of...well, it.

Dusk’s member, big and black and thick, had pushed its way out of his sheath overnight—or maybe it had never retracted. It arced over his stomach, the flare hovering somewhere above his upper chest. Easily as wide as one of Dusk’s legs, it was easily twice Shining’s own length. The difference in girth wasn’t even close.

A massive nutsack sat right at the base of Dusk’s crotch. Each one of his testes was more than half the size of Shining’s head, and were fatter, rounder, and plumper than any that Shining had ever seen. Shining found his head spinning as he tried to conceive of just how much cum Dusk’s massive orbs could hold. Then, his eyes darting up, he realized that he didn’t have to try.

The ceiling was absolutely splattered with a thick layer of white. It didn’t take Dusk’s genius to determine that it was the source of the overpowering musk. What had to be easily gallons of caked jizz covered the ceiling—and the walls, and the carpet, too, Shining noticed, gulping. The headboard had been painted—or rather, stained—white, fat globs of Dusk’s pleasure stuck onto the fabric.

Dusk’s snoring was louder with the door open; it was like the rumbling of a train engine: low, constant, pervasive. Shining felt his body vibrating to the rhythm of Dusk’s massive body, his crotch stiffening, throbbing in time to the twitches of Dusk’s enormous shaft.

A bead of pre the size of a golfball had beaded at Dusk’s tip. It dangled over his chest for a moment—then plopped down onto his fur, joining the small lake of precum that had been matting his fur throughout the night. Even from here, it was easy to tell that Dusk was at full mast. And even after last night! Shining didn’t even know how many times his “little” brother had gotten off last night, but from the looks of his room, it was more times than he could even imagine. And he looked even bigger today.

It was obvious that Dusk was going to wake up with one hell of a case of morning wood. As if on cue, Dusk groaned slightly, shifting his weight. His right hindleg twitched across the mattress, making the bed’s springs creak in protest at his weight.

Shining reacted instantly. By pure reflex, his magic yanked the door closed. It was only by pure luck that he managed to remember to close it softly, rather than slamming it shut. The door clicked into place, not as softly as when he’d opened it, but much, much more quietly than it could have.

Shining stared at the blank white door for a moment, his chest heaving. Had he really just—no, but he hadn’t done anything—but why did he want to; no, need to—but he couldn’t think about Dusk like that, had to resist the urge to stare at him, to watch his growing, unconscious body. Shining clamped down on that urge, hard, and forced himself to march off back to the bathroom, his newly sprouted erection slapping against his thighs the whole way.

He refused to jerk off that morning, no matter how stiff his crotch got. He couldn’t let Dusk be that kind of stimulus for him—couldn’t let himself keep thinking of his brother like that. And he was supposed to be the bigger brother—why was he so fascinated with Dusk being bigger than him?

Or, he thought, a creeping shudder going down his spine, so fascinated with himself being smaller than Dusk?

Today was a Saturday, which meant no school. Today was a Saturday, though, and that meant Shopping Day.

Mom was too busy to pick up groceries—something about a weekend conference—and Dad was just feeling lazy, so Shining found himself kicked out of the house with a pile of grocery bags and a pouch full of bits. Dusk was with him.

They weren’t quite at the point where Dusk had to duck to get out of the front door, thankfully. All the same, it was hard for Shining to ignore just how much space his brother took up—how his broad shoulders were nearly rubbing the doorframe, how his horn just about scraped the top of the molding. When Dusk stepped fully outside, his full size towering above his brother, Shining almost felt relieved. At least out here, he wouldn’t have to be reminded of how much of a doll house the house was becoming to him.

“So, Shining,” Dusk said, trotting down the street. For him, it was a moderate pace, but his strides were now so much longer that Shining had to nearly jog to keep up. “What’s on the list?”

“Food, mostly.” Shining did his best to keep his eyes on Dad’s grocery list, though it was impossible to ignore the shadow his brother cast over it. “Lots of veggies. Plus some toiletries.”

“Mm.” Dusk licked his lips. “I could go for some veggies right now.”

He’d just eaten breakfast an hour before—complete with a portion size as large as the rest of the family combined. Shining wisely kept his mouth shut.

“Okay,” Shining said, telekinetically rolling up the list. “I think we should be able to get most of this stuff in Canterlot Square.”

“Sounds like a plan,” Dusk said. “Lead the way, big brother.” Shining heard the twist in the last two words, but chose to ignore them.

The Canterlot Square was always a crowded part of the city, and doubly so on weekends. Ponies filled the pavilion, which itself was as long as two hoofball fields. Everywhere Shining looked, there were more vendors hawking their wares: Fruits, sweets, jewelry, clothes. He spotted a soft-looking pink scarf at one stand, and made a mental note to come back later to pick it up for Cadance.

The crowd on any other day would have been stifling. Today, though, with Dusk at his side, Shining found the crowd giving them a wide berth. It didn’t seem to be a conscious thing, really—it just so happened that a stallion of Dusk’s size cut through crowds like a horn through butter. Ponies just unconsciously flowed around him, like water around a boulder, his head poking far enough above the rest of the crowd that anypony could have seen him coming from halfway across the Square.

Their first stop was at a fruit vendor that Mom liked. Shining ordered a half-dozen apples; after looking up to see the hungry glint in Dusk’s eyes, though, he tripled the order. He had a sinking feeling that they’d need to pick up more by tomorrow, anyway.

Fortunately, finding the rest of what they needed was fairly easy. Shining and Dusk had been coming here to shop for most of their lives, after all. Shining Armor was grateful for that. He was happy to be out of an increasingly Dusk-dominated house, but all the same, the stares that they were getting were making him increasingly uncomfortable. It wasn’t like they could stop it, though—Dusk was just big, and that kind of size tended to attract attention.

It wasn’t until Shining scratched off the halfway item on the list, though, that that attention started to go south. At first, Shining couldn’t hear it over the din of the crowd around him, but as time passed, he found the sound growing louder: a steady, meaty thwack-slap sounding off repeatedly as they stepped through the square.

Oh, no. It couldn’t be. But—oh, geeze, it was coming straight from Dusk. Almost completely unwilling to look, Shining forced himself to glance to his side, already fearing what he might find.

Dusk’s stallionhood had slipped out of its sheath, and was now dangling below his belly. Even soft, it was almost as long as Shining’s was hard, and it wasn’t going to stay flaccid for long. Even in the two seconds that Shining turned to watch it, he saw it shudder, throb, then stiffen until it was a good two inches longer than when he’d first seen it. Behind it, a pair of fat, plump balls that dangled down to Dusk’s knees dropped down behind his tail, swaying and slapping against his legs with each long step he took.

Shining had gotten erections in public before—it was an awkward, private sort of thing, but a stallion could usually conceal his beneath his underbelly until it went away. Dusk, though, had no such possibilities available. At more than a head in height taller than the tallest ponies in the square, the bottom of his belly was level with most shorter ponies’ heads, exposing his growing boner to most anypony who passed them by.

Shining swallowed, desperately trying to keep his eyes pointed forward. He’d forgotten which stand they’d been headed to, and now only wanted to hope that Dusk’s arousal would just...go away. Still, it was clear that that was anything but the case. Dusk’s stallionhood continued to stiffen, his shaft lengthening, his girth widening, until his member poked up all the way to the bottom of his chest. Every push of his hips forward sent his oversized organ slapping up against his underside, his wide flare bouncing and swaying as it became visible to literally anypony standing in front of him.

“Hey, Dusk?” Shining asked. He made sure not to make eye contact.

“Yeah, Shining?” Shining heard Dusk swallow, could hear the straining growing in his voice. “What’s up?”

“You feeling okay?”

“Fine,” Dusk said—a little too quickly. “Just fine.”

“If you’re not feeling well, we can just head home—”

“No!” Dusk said, forcefully. Then again, somewhat softer: “I mean, no. Really. I want to finish this up.”

“Okay,” Shining said doubtfully. His nostrils flared. He could already smell Dusk’s musk seeping from his growing erection. It was driving him crazy, too—even awash in the scents and sounds of the largest Canterlot pavilion, Dusk Shine’s smell still found a way to fill his lungs, to heat his crotch, driving his every breath shorter and sharper. Crushing that thought and ignoring the growing stirring between his own legs, Shining double-checked the list and directed Dusk toward the next stall: a stand selling fresh produce from around Fillydelphia. Mom loved their celery—just couldn’t get enough of it. He had a feeling that Dusk couldn’t get enough of it either, though probably not for the same reasons.

As they approached the stall, Dusk’s shadow fell over the shopkeeper, blocking out the sun. The older-looking mare blinked, then glanced up—and paled. The largest stallion she’d likely ever seen grinned awkwardly down at her, his oversized frame filling out most of the stall.

Shining managed to squeeze himself in beside him. “Excuse me,” he said, clearing his throat and hovering the list forward. “We’d like to buy some of your celery. And some potatoes, too, if you have them.”

The mare’s eyes tracked down over Dusk’s neck, his chest, and then—widening—the fat flare dangling between his legs. She licked her lips, still staring forward. “Ah. Yes. Well, I should have some potatoes in the back—let me go check. And you can help yourselves to the celery in some of these crates.” She made a halfway sort of nod toward the produce-filled crates laid out beside the stand, though it was clear her heart wasn’t in it.

“Thanks!” Dusk said. His voice rang out unnaturally loud in the stall’s cramped space. With a small “eep!” the shopkeeper darted back away from the counter and slipped behind the curtain separating the back of the stand.

Dusk blinked after her, blushing. Shining just sighed. Rounding the counter, he stopped over the celery crate and picked a few up in his magic. Dusk followed, his heavy footfalls shaking the ground around the stand slightly. At this size, he was anything but subtle.

Shining pretended to inspect the celery, but really, all his peripheral attention was directed at Dusk. He could hear his brother’s breathing growing deeper, Dusk’s breaths becoming short gasps, and then pants, as whatever arousal had seized hold of him mounted even higher.

“A-ah!” Dusk gasped, his eyes squeezing shut. His hips bucked forward, his erection slapping up against the bottom of his chest. A glob of precum half the size of most of Shining’s entire loads burst from his tip, splattering all over the crate’s contents.

A split second later, the shopkeeper came bustling back out of the back, a crate of potatoes balanced on her back. “I did manage to find some, dears,” she said. “I just want to let you know that—”

Her voice trailed off, her eyes widening even further when she saw the mess Dusk had left. Blushing furiously, Shining yanked out the purse and spilled a pile of bits onto the counter.

“We’ll take the whole crate,” he blurted. Dusk’s stomach grumbled, and Shining dumped a few more bits onto the table. “And the potatoes, too.”

“Ah—I—yes.” The mare just kept staring at Dusk’s ‘leavings,’ looking as though she were trying to ignore the evidence of her eyes. As if on cue, Dusk’s shaft flared again, spurting an even larger load of precum all over the already-dripping pile. “Of course.”

“Thanks!” Shining said quickly. He grabbed both crates in his magic—there was no way they were going to fit in the shopping bags—and turned to leave. “Thanks for the sale; have a nice day. C’mon, Dusk; let’s go.”

His cheeks still flushed red, Dusk turned to go after him. Though he hadn’t had to duck when they entered, the top of his head now scraped against the top of the stall’s roof. They left the shopkeeper staring after them, her glasses slowly slipping down her muzzle, as she watched Dusk’s massive, fat balls smack against the insides of his legs with each step he took. A trail of clearish-white liquid lagged behind them, Dusk’s arousal still spilling copious amounts of pre as his member lurched and shuddered.

Ponies had noticed them before, but now everypony was staring at Dusk. Shining did his best to just put one hoof in front of the other, keeping his eyes pointed straight forward as ponies around them murmured and pointed at Dusk’s oversized member, at the fat, heavy nutsack that his swaying tail did absolutely nothing to hide. He imagined them pointing at him, wondering why he was so much smaller than his brother, wondering why the “bigger” brother’s stallionhood was nearly as long as his “little” brother’s entire torso.

Dusk’s breathing was getting worse, too—he sounded like he was wheezing, gasping for air. The strain on him was obvious; Shining felt his blood run cold when he imagined just what Dusk was struggling to hold back. Then he remembered his brother’s “activities” from the night before, and just how much he’d produced—how much, and how many times he’d had to produce—and imagined no more.

A growing stallion had a growing libido, after all.

Dusk’s nostrils flared steadily, his limbs trembling as they made their way down the side of the Square. Shining would almost swear he could hear his brother’s nuts churning beside him, sloshing as Dusk’s cock slapped against the insides of his forelegs. He kept himself from looking at them—just barely—but knew that they were there: a pair of huge, heavy cum-filled orbs so big and musky that he could just bury his muzzle in them.

It wasn’t for another fifteen seconds that Dusk broke, but the incident was one that Shining would remember for a long while. It was an innocent motion—Dusk, unaccustomed to his new size and stride, stumbled, and nearly tripped. He twisted to one side, his hip curving toward Shining—and letting his engorged erection rub against Shining’s side. Shining’s eyes widened as his little brother’s big erection left a dripping trail of precum matting his fur, but Dusk actually moaned.

That did it. The second Dusk’s hooves touched the ground, his shaft throbbed, splattering the ground with a puddle of precum as wide as Shining’s head. Dusk gapped, his nuts churning audibly as he gasped, “Where’s the bathroom?”

Everypony was watching them—what their expressions were, Shining didn’t want to know in the slightest. He was too busy trying to control his own mortification. “Uh. I don’t think there’s a public one nearby, but—”

“Never mind,” Dusk blurted, and rushed off to the side. He galloped through the crowd his huge stride covering distances longer than most ponies’ bodies as he shot toward an opening in the stalls just barely wide enough for him to fit. His cock slapped against his belly with each bound, spurting huge globs of pre as his mounting arousal reached a peak.

Shining just barely managed to catch Dusk slipping into an alleyway before his brother vanished from sight. Pushing his way through the crowd proved to be more difficult without a seven-foot stallion to break the surf for him, but Dusk had already cleared a wide berth, actually having knocked over several ponies in his desperate escape. Shining galloped after him, his mane flying behind him as his own mounting erection stiffened between his legs.

He heard Dusk before he saw him—a loud, roaring moan interspersed with grunts and gasps. “Ah—ah—aah!” Then—

Shining rounded the corner just in time to see Dusk, his forelegs propped up against the alley wall, cry out as his hips bucked forward. His monstrous shaft, which was fully engorged and throbbing heavily, bulged visibly before lurching, unleashing a load of cum that had to be at least a gallon in volume.

It all splattered against the wall, stains of a thick, creamy, white covering the bricks and slowly dripping down to the ground. It wasn’t long before a second gallon joined the first, Dusk’s cries of pleasure bouncing off the alley walls as he absolutely drenched the ground and sides with his seed. The wall actually shook as he slammed his hoof against it, his whole body twisting with the force of his orgasm as his third load burst against the wall, bigger in volume than the first two combined.

Shining whirled back away from the carnal scene and flattened himself against the wall. He stared at the back of the stall before him, his chest pumping up and down while his heart went doubletime. Oh, fuck. He’d seen Dusk’s leavings—had seen him in all his glory—but he hadn’t seen him like this, so incredibly virile, big that even his arousal was huge, his uncontrollable libido covering his surroundings with impossible amounts of his size-fueled spunk.

He himself was hard—incredibly so, even. Shining let his forelegs drop to the ground just as a fourth splat! echoed out from the alley, Dusk’s labored breathing mixing with his moans. Shining couldn’t—wouldn’t let himself lose control, wouldn’t give into his own arousal now. He had to deny that he was turned on, couldn’t allow—not like this. And yet he couldn’t help but stand there, frozen still, as he remembered just how close Dusk’s front hoof had been to the second-story window when he’d been leaning against the building.

Another half-minute later, Dusk finally re-emerged from the alleyway. He’d evidently used magic to clean up, Shining noted as he peered past Dusk’s shoulder, though a dumpster a bit further down looked to be overflowing with a white, creamy liquid.

Shining swallowed, steadied himself, and then looked up at Dusk. All the way up at Dusk. His brother’s head towered above him, his big body covering Shining’s in its shadow.

Shining coughed. “So, uh—all done with your, ah, bathroom break?”

Dusk blushed furiously. “Yeah,” he muttered, glancing to the side. The stares from the crowd seemed to almost overwhelm him. “Uh—sorry.”

“No problem.” Shining definitely wasn’t making eye contact right then. “Um. Good to go?”

Dusk coughed as well. “Let’s.”

Chapter Three: Out In the Open

Shining Armor was panting.

His breaths came in short, sharp gasps, his chest puffing up and out as he pushed his head harder against the back of his bed. Above his muzzle, his horn glimmered blue; a sheath of cerulean magic had wrapped itself around his stallionhood, squeezing it tight and pumping itself up and down his length.

Shining Armor squirmed, his tongue hanging out of his mouth as he went to town on himself. His magic took care of the upper half of his shaft, but he’d wrapped one of his hooves around the base, jerking off his girth as hard as he could. His other hoof massaged his heavy, full nuts, which were more than ready to spill their seed.

He’d held off as long as he could—resisted the urge the whole time he and Dusk had been walking back from the market. But by the time they’d gotten home, Dusk had been hard again, and the second they’d tromped upstairs, Dusk had slammed himself into his room and just moaned. Shining’s whole body had gone stiff, erect in that moment, and before he knew it he’d closeted himself in his room as well. The door hadn’t been shut for a second before he’d flopped onto his bed and started humping his mattress like a mare in heat.

Turning over onto his back had provided more control, his hooves and magic working overtime to stimulate every part of him at once. But Shining didn’t need that stimulation—didn’t, couldn’t have any control. The only thing in his mind was an image of Dusk: huge, horny, growing bigger and bigger and more virile than he could even imagine.

How could he have ever thought that he was a real stallion? Next to Dusk, Shining’s “big brother” status looked like a joke—all that size, all that power, all that lust. Shining was panting, jerking himself off harder now as his fantasies went to his head. He saw in his mind’s eye Dusk’s cock bouncing ,swaying between his legs, his massive nutsack dropping further and heavier as his body swelled to fill the whole house.

He wanted that—he needed to be that. He’d never known it, but Dusk was rapidly becoming everything Shining Armor had ever wanted to be and more. Shining’s grunts turned to snorts, his moans becoming whines as his arousal mounted rapidly. His magic and hoof made loud schlick-schlick sounds as they pumped across his length, the stream of precum dripping down his member rapidly lubricating his shaft and crotch.

Dusk had always been so small—but now, he was larger than life. Shining squeezed his eyes shut, picturing Dusk in the forefront of his mind. How he wished, down in some deep dark place he could never admit, that Dusk were here now, big and huge and filling up his field of view. How he wanted—needed, really—to feel his body’s huge weight, to hear his lower, rich voice deepen as his body swelled to new heights.

There was a rap on the door. “Shining?” Dusk’s voice echoed through a crack in the door. “Can I come in?”

Yes—just like that. Lost in the realm between fantasy and lust, Shining found himself nodding along, grunting as he wove Dusk’s voice into his daydream. “Yes,” he panted, groaning, “Yes, yes, yes!”

“Okay,” Dusk’s voice said. “I’m coming in.” And the door started to open.

Too late, Shining’s eyes snapped open, registering reality for the first time—but there was no time to stop himself. His cock was already spasming, his erection throbbing, his balls tightening against his groin as he began one of the messiest, most intense orgasms he’d ever had in his life. As Dusk’s big head poked through the doorframe—actually bending down, so that he could fit through—Shining’s body was already shaking, quivering as his shaft shot rope after rope of thick spunk over his chest.

It seemed impossible that Dusk hadn’t noticed yet. Shining watched him out of the corner of his eye, a dawning horror in his stomach, as his brother squeezed himself through a door that was obviously far too small to fit his frame. His shoulders scraped the sides, the top of his horn scraped the top—and that was with him crouching down, his bulk struggling to fit through the door. The realization that his “little” brother didn’t even fit through doors anymore just drove Shining’s orgasm to new heights. He was powerless to resist as his voice peaked into a cry of pure, helpless pleasure, his hips jerking and knees spasming as the largest load he’d ever cum splattered all over his chest.

And then Dusk was standing over him, just barely fitting between the end of Shining’s bed and the far wall. Shining’s chest heaved, his eyes wide, unseeing, as a last glob of cum dropped from his tip, splattering onto his jizz-matted chest.

He was covered in his own seed—he’d never cum harder in his life. One glance up, though, brought the horror roaring right back—Dusk was watching him, staring down at him, his lavender cheeks burning as red as a charcoal fire.

“Oh, gosh,” Dusk stammered. “Oh, geeze—I should have knocked louder. I’m so sorry—I—didn’t think—I—”

He turned to go—and Shining slapped both hooves over his face. “Agh!” he groaned, his mane falling over his eyes. “I can’t deal with this!”

Dusk stopped. Slowly, as if he was moving through molasses, he turned to face Shining. He couldn’t quite meet his “big” brother’s eyes, instead opting to stare at a speck on the wall around a foot above the bed. “What do you mean?”

Shining groaned again, and pushed his mane out of his face. He slung his hindlegs over the side of the mattress and rested his arm in his lap, around his still dripping shaft.

“Just—you,” he muttered. “This growth spurt—I can’t stop thinking about it. You’re just getting so big, and I can hardly keep it off of my mind. I can’t stand it—how big are you going to get? Why is my little brother so much taller than me? How is this even possible?”

He choked on the last word, then flopped back onto the bed, his hooves splayed out around him. Out of the corner of his eye, he could see Dusk’s big shape fidgeting slightly.

“Well,” Dusk said, after a moment. His voice sounded slow, awkward. “If you’re wondering about how...I might be able to help.”

Shining pushed himself up off of the bed. He stared up at Dusk. “How?”

Dusk coughed. “Well, when this started happening, I did what I always do.” He blushed slightly. “Research.”

Of course.

He sat down, his thick, muscled haunches pushing out around him as his flank hit the carpet. The second-story floor actually shook under the impact. Even sitting down, he was still taller than Shining was standing, now. Somehow, Shining just took that for granted.

“I went to look at the library to see if there’d been any studies on adolescent stallions and puberty,” Dusk said. “Of course, there were, but I decided to get a little more specific. I looked up unicorn stallions, specifically, and that just pointed me toward a study done a few years back on magic-fueled development.”

Shining blinked. “Wait. You mean that this is your magic doing this?”

“In a way.” Dusk shrugged his big shoulders. “It turns out that all unicorn stallions go through a brief period of development around my age—kind of a magic-fueled puberty, in order to compete with natural earth pony development patterns. Usually, that period takes around a month or two, and only adds on one or two inches at most. I think you gained four, which is actually kind of an outlier.”

Shining did remember that. He’d been proud of it, especially when Mom had started to celebrate her firstborn son “growing up.” It’d been a great feeling—but nothing, he guessed compared to what Dusk had been going through lately.

“Wait,” he said. “Then how did you get so big?”

Dusk shifted his weight, looking a bit embarrassed. “Well, the amount of growth is proportional to the amount of magical energy in that pony’s internal font. More natural magic means more fuel for the body to grow—energy is mass, right? Or rather, vice-versa.” He chuckled awkwardly, scratching the back of his neck with a plate-sized hoof. “It’s actually a rather complicated process. But the general idea is that more magic equates to...well, a bigger growth spurt.”

Shining just stared. He looked up at Dusk, taking all of him—all seven-plus feet of him. He had to be taller than seven feet by now—the doorways were seven feet tall, and Dusk had had to bow down almost to his shoulders to fit in. Even now, sitting down, the top of his horn was just a foot or two away from the ceiling, and that was nine feet tall! Shining swallowed, steadying himself.

“How much magic does that even take?” he said. He swallowed, his throat feeling dry.

At least Dusk had the grace to look embarrassed. “Um. A rather lot, as it turns out. There’s a reason why Princess Celestia took me on as her student as a colt—I think my magical font is somewhere on the level of orders of magnitude larger than yours.”

Orders of—Shining’s head was spinning. And with a size that big, Dusk’s magic had to be stronger than that of the Princess herself. Struggling to hold himself together, Dusk just pulled himself back up to a sitting position.

“Okay,” he said, keeping his words even. “I guess that makes sense. But—agh! You’re so big in all the other ways. Did you really have to be big there, too?”

“I’m sorry!” Dusk said quickly. “I didn’t ask for this.”

“Don’t apologize,” Shining snapped. “I don’t mind it. Really. I just…”

He froze, his voice perched on the edge of his next words. Trembling slightly, Shining squeezed his eyes shut, and said, “I just really, really like it.”

He’d spoken as quietly as a mouse, but his words seemed to ring through the quiet room with all the subtlety of a sledgehammer. Dusk stared at him, Shining’s skin crawling as his brother weighed, evaluated, calculated, his big body seeming to fill up more of the room with each breath her took.

“You—like it?” Dusk said. “I thought you were embarrassed by it.”

“I was—oh, damn it. I don’t know how I feel.” Shining squeezed his eyes shut even tighter, refusing to look at his bigger little brother at all. “I just know that I look at how big you are, and I imagine myself being with that—or being like that—and it just drives me crazy.”

“Crazy—” Dusk actually gasped. “You mean—what you were just doing—you actually.”

“Yes,” Shining bit out, miserably. “I was getting off to you, okay? Fuck!”

That brought the whole room to a silent, screeching halt. Shining didn’t curse lightly—and especially not to his younger brother. But he couldn’t help it—all the strain, all the inadequacy, all the arousal of the last few days was just exploding out of him.

It felt good.

“I—” Dusk sounded uncertain. “I—really?”

“Yeah,” Shining said. He took a deep breath. “That’s what I was doing, okay? I just couldn’t stop thinking about how big you were, how big you were getting—and I’d been keeping myself from jerking off to that for so long, but I finally just couldn’t help it. And then…” He glanced down at the mess on his chest, shrugging. “And then this.”

Dusk nodded, swallowing. “...You’re still hard, though.”

Shining blinked. “I—what?”

He looked down. Dusk was right. Despite the explosive orgasm he’d just had, Shining’s shaft was as hard as ever—harder, even. A line of precum had already started running back down the side, his balls filling up again and pushing against his thighs. Shining stared at his stiffening boner, then grunted, his eyes fluttering shut as his erection throbbed.

Dusk’s voice was small. “Do I—really turn you on that much?” he asked.

Shining stared at his lap. “Yes,” he said. “Yes, yes, yes.” Just being here—with Dusk in the room—he hadn’t, couldn’t have imagined how much having this all out in the open would turn him on, but he’d be damned if he could help it now.

“Then—” And then Dusk stepped forward and leaned over the bed, The weight of his massive hoof pushed the mattress down, his shadow falling over Shining’s body as he leaned forward. Then his mouth opened, his lips parting as Shining’s eyes widened. And then he all but melted into the mattress, his whole body going limp as Dusk’s lips closed around his erection.

Dusk slurped at him once, his big tongue licking up a good amount of Shining’s leakage. Then he pulled back, licking his lips slightly. “—what about that?”

Shining just stared up at him. He was trembling, he realized, his hind legs twitching. He thought he could hear the blood pumping through his ears.

“What—” he began, almost in a whisper. “You—but—”

Now it was Dusk’s turn to look away. “I, uh,” he said, “may have been in a similar position to you. Before, that is.”

“Before—” It took Shining a moment to get it. “To me?”

“Yes!” Dusk blurted. “You were just so tall—you were one of the biggest stallions I’d seen. You were so confident, so big, and you had Cadance, and you were my big brother and—” He slammed his muzzle shut, his jaw trembling.

It took Shining a moment to take all that in. “You mean—even before all this, you—” He cut himself off, then gave the throbbing shaft between Dusk’s own legs a meaningful look. Both stallions’ modesty was rapidly evaporating; at the sight of Dusk’s massive stallionhood, Shining’s own crotch stiffened further.

“Um. Yes.” Dusk’s blush was adorable. For a moment, Shining almost felt like they were colts again—and then he realized that he’d been ogling his brother’s oversized cock for the past ten seconds, and blushed as well. “I wasn’t trying to be weird or anything—I just...imagined myself being like you. Being as big and strong as you. And now…”

Shining couldn’t help but chuckle. “Guess you got what you wanted, huh?” When Dusk nodded sheepishly, Shining shook his head. “I guess it feels pretty good, huh?”

Dusk’s head bobbed up and down eagerly. “Oh, it feels fantastic. And growing feels even better—it’s like nothing I’ve ever felt before—and, well…” He trailed off, his cheeks still red.

“What?” Shining asked.

“Well,” Dusk said. “I, uh...wanted to ask. Did that feel good?”

Shining blinked up at him. “What do you mean, ‘that’?” He followed Dusk’s gaze to his crotch and dripping erection. “Ah. That.” Swallowing, Shining grinned over at him. The mattress sunk a bit under him as Dusk leaned a little bit more of his weight onto his front hoof. Dusk was only a few feet away from his crotch, now, but in his mind, it felt like mere inches. “It felt...good. Really good. But I’m not sure if you should do it again?”

“Why not?”

“Because we’re brothers!” Shining blurted. Silently, he thanked Celestia that their parents weren’t home. “Because we’re not supposed to do that!”

“But we both want to.” Dusk’s words shut Shining up fast. “We’ve both wanted to. And...well, you’ve said that you like me like this.” Dusk blushed even more adorably, his oversized ears flitting forward and backward. “And I like doing that to you. So if it feels good...why not just go with it?”

Shining took a deep breath. Then he cracked another tired grin up at Dusk. “It’s weird not to have you overanalyzing all of this for a change.”

“Oh, don’t worry.” Dusk beamed down at him. “I’ve done plenty of analysis over the past few days. It just happened to be at the same time, or immediately after, ah, certain...personal activities.”

“Got it,” Shining said. He inhaled slowly, then nodded. “Screw it. If it feels good, right?”

“Right.” Dusk nodded down at Shining’s crotch. “So...may I? ‘Big brother’?”

“Little brother is more appropriate by now, I think.” Shining smirked at him. “But go ahead.”

Dusk stood still for a moment. He stared down at Shining’s erection—pitiful compared to his own, though Shining thought he saw a flicker of fascination behind those bright purple eyes. He seemed to be weighing something, calculating, debating.

And then, the mattress sinking under the weight of his hoof, he leaned forward and gingerly took Shining’s member in his mouth.

Shining shivered as Dusk’s muzzle closed around his girth. Cadance had always had some difficulty taking all of his length—when they’d started experimenting, she hadn’t even been able to fit his flare all the way in—but Dusk swallowed more than half his cock without even blinking. Shining’s breath caught in his chest, his hind legs going stiff as the big stallion before him slowly rolled his lips up and down his length.

Dusk seemed to be experimenting, exploring. Which made sense—given his age, and his, well, physical state before now, any kind of sexual contact with another pony had to have seemed off-limits to him. Now, though, his eyes were bright, his lids fluttering thoughtfully as he tasted Shining’s girth. Shining moaned softly, his hips jerking and sending a glob of precum to splatter against Dusk’s gums. Dusk just tasted it, his big tongue dabbing into the puddle of pre in his mouth, then turned back to let his tongue roll up and around Shining’s head, embracing it in a perfect cocoon of soft, warm, moist flesh.

Shining was breathing heavily now. “A-ah,” he grunted, his eyelids fluttering. “Dusk—oh, that feels so good.” He was panting a bit, his eyes jerking shut as Dusk went all the way down to his base—first straight down, so that Shining’s normally massive length just went back to the end of his mouth, then sideways, turning his head and pushing Shining’s shaft with his tongue so that it swished against the inside of his cheek, deforming and bulging it out slightly. “Nngh,” Shining groaned, watching his flare prodding against the inside of Dusk’s cheek. “Oh, gods, Dusk, don’t stop.”

Dusk just glanced up at him. Shining could swear that his little brother’s muzzle curved upward into a smirk. Then, Dusk began to pick up the pace. He kept eye contact with Shining for a few moments, but then turned back to his task. He bobbed his head up and down, his lips smacking against the sides of Shining’s organ as he rolled his muzzle over Shining’s girth. Shining panted, squirming as Dusk swallowed his cock again and again, letting it slide past the opening of his throat before pulling back.

Streams of precum were spurting from Shining’s cock; Dusk gulped them all down, eagerly even. Shining imagined Dusk swallowing his cum, then using it to grow even bigger, until he could hold Shining’s entire cock in his mouth without even trying. That just turned him on even more, increasing his output of pre and giving Dusk an even bigger meal to swallow.

Shining had both his hooves on Dusk’s broad shoulders, feeling Dusk’s massive weight rock a bit back and forth each time his head bobbed down over his crotch. He felt like a foal cradling an adult stallion, like a midget trying to direct a giant. “Keep going,” Shining grunted. “I’m—almost there. Oh, fuck.”

Dusk picked up the pace. He suckled even harder at Shining’s cock. The suction was insane. Shining actually had to grit his teeth, squeezing his eyes shut as Dusk’s big, inviting mouth took over, swallowing up his stallionhood and controlling it completely. Dusk’s big tongue swished along his underside, controlling his shaft’s every movement. Every time Dusk’s lips kissed the bottom of Shining’s shaft, they pressed down on his balls, plumping his heavy nuts and increasing the frequency of the pre spattering against the insides of his cheek.

Shining was getting there, and he was getting there fast. Scarcely a full minute after Dusk had began suckling on his member, he felt his hips jerking faster, his face contorting as he gasped for air. “I’m—” he gasped, sweat rolling down his cheeks. “I’m gonna—I’m gonna cum. I’m gonna—ngh!”

He gasped as the tension in his loins went slack. His muscles tightened, forcing his hips upward against Dusk’s muzzle. Shining felt the head of his shaft flare between the curl of Dusk’s long, oversized tongue, the first ropes of his load shooting out and splattering right against the back of Dusk’s throat. Shining groaned, his hooves clamping around Dusk’s muscular shoulders as he went over the edge, his hips violently jerking as his member burst with copious amounts of ejacluate.

Dusk just drank it all down, his big cheeks puffing thoughtfully as he gulped shot after shot of Shining’s load. Shining was breathing heavily by the halfway point, his mane feeling hot and damp over his face as his flaring member gushed more and more jizz into his brother’s mouth. He’d already cum today, but the intensity of this orgasm surprised him—it almost matched the first in terms of sheer strength, and the volume was insane. The suction of Dusk’s lips around his shaft, though, only increased the output of Shining’s heavy nuts; he felt like he were being milked, as though Dusk were gulping down swallow after swallow of his hot load in order to grow bigger than ever before. And he loved it.

When Shining finally finished, he was wheezing, sweat streaming down his chest. Dusk just pulled back, the edges of his lips coming off of Shining’s cock with a wet pop. He inhaled slowly, the force of his breath actually pulling Shining’s thoroughly wet shaft a few centimeters forward, and then glanced up at his once-”big” brother with a hopeful, curious look.

Shining released his grip on Dusk’s shoulders and slumped back, his hooves sinking deep into the mattress. “W-wow,” he gasped, his chest heaving. He shuddered as the afterglow of release spread through his veins. “That was...incredible.”

Dusk gave him a shy smile, leaning his head on the edge of the bed. “I’m glad you liked it.” It was funny how, when he folded himself in like that, it was almost like talking to a shorter Dusk—but then Shining saw the tall, muscular curve of his brother’s flank rising above his head, and the illusion vanished.

“Very much so.” Shining closed his eyes and drew a slow, shuddering breath. “Wow. Thank you.”

“Glad to help. You looked pretty hard.” An awkward expression crossed Dusk’s face, and he glanced down off to the side, his cheeks reddening again. “Actually, uh…”

“Yeah?”

“I, uh, may have gotten a little excited during that too.” Dusk forced a smile. “It’s not every day you get to suck on your big brother’s cock, right? So, uh, well…”

He pushed off of the mattress, drawing himself up to his full height. The top of his horn nearly scraped the ceiling like this, his broad shoulders flexing as he ascended to his full size. At his height, around six to ten inches of space were visible between Dusk’s underbelly and the top of the bed. Shining stared, eyes widening, as a very large, very hard shaft bobbed between his brother’s legs, drooling a veritable river of precum onto the ground.

“Uh,” he said, licking his lips. “I don’t think I’m going to be able to fit that into my mouth, Dusk.” The flare alone looked as wide as his whole head.

“Oh! Right.” Dusk blushed even harder. “I was just thinking, though—maybe you could, I don’t know, rub it a bit? It’s just so hard, and my balls feel so full—”

“Even after the show you gave today?” Shining said. He could, in fact, see Dusk’s balls past the girth of his head: a pair of huge, fat black spheres dangling to just below his knees. He could imagine them sloshing, groaning with cum as they produced more and more jizz than any other stallion could handle.

“Yeah. At this size...well, I tend to have to ‘relieve’ myself once every few hours. If not more often.” Dusk chuckled, made to scratch the back of his neck, and wound up back-hoofing the ceiling instead. He blinked up at it, looking awed and surprised at his own size. “Five or six orgasms a day has gotten to be kind of the norm for me—and that was just yesterday. Today, I’m even bigger, so it’s a lot harder to handle.”

“I’ll bet.” Shining just stared. The amount of pre pouring from Dusk’s slit had run onto the carpet, staining it, and pooling into a big, whitish-clear puddle. It looked like his brother had already leaked more than Shining had gotten in his entire last orgasm. No wonder Dusk was so desperate to get off.

“Alright,” Shining said. He was unable to tear his gaze away from Dusk’s massive erection. “How do you want to do this, then?”

“Well,” Dusk said. “I was thinking we could…”

Instead of finishing his sentence, he turned, then flopped down onto his back. The whole floor shook as Dusk’s quarter-ton body impacted onto the carpet, Shining’s bed especially trembling on its supports. Dusk grinned sheepishly up at him. He had his forehooves curled up against his chest, his hind legs planted firmly on the ground. Above his belly, his massive stallionhood bobbed helplessly, drooling steadily onto his chest.

A blush on his face, Dusk said, “I thought this might be...a bit easier?”

Shining was blushing too. Dusk easily covered most of the distance from the door to the far wall—he seemed to fill up most of the room without really trying—but this new position just seemed so...vulnerable.

Hopping off the bed, he evaluated Dusk’s position for a moment. Then he shook his head. “I don’t know. You’re a lot bigger than me, but not that much—I don’t think I’d be able to balance on your stomach or anything.” His cheeks flushed red, Shining added, “But maybe if you, uh, sat up or something? Then I could try that.”

Dusk nodded. Scooting himself back a few feet—and setting the whole floor shaking again—he pulled himself up into a sitting position. As he inched his way up the wall, his head towering up toward the ceiling, his cock slapped against his chest, then flopped heavily onto the floor. Shining looked down it and took a deep breath. Even sitting down like this, Dusk was a good foot taller than him now—had he gotten even bigger in the last five minutes?

Tentatively, Shining stepped forward. Dusk’s cock was about as thick as his torso, and around as tall. His balls—Shining could barely even comprehend their size. Each one had to be a good two feet in diameter; he didn’t even want to think about how much of Dusk’s seed they held, especially given how much he was drooling right now. Or maybe, he decided after a moment’s reflection, he absolutely did.

When Shining’s hooves, tiny by comparison, made contact with Dusk’s flare, the larger stallion actually moaned a loud. Dusk’s breathing was different than Shining’s had been—long, slow, and labored—but the evidence of arousal was perfectly clear. The leakage of pre doubled as Shining’s hooves gently rubbed around Dusk’s head, the soft fur of his fetlocks teasing the veins running down his length.

“Oh, wow.” Dusk shuddered, his eyes fluttering shut for a moment. “No wonder I went off like that earlier.”

Shining kept rubbing. His hooves went a little further down, then a little further up, massaging Dusk’s girth as his own body pushed forward and back. “Hm?”

“At the market,” Dusk said. “When I—ah, touched you.” His cheeks coloring, he said, “I’d never felt anything like that before. Touching myself had always felt good, but when I brushed against your coat—I never knew how good touching another pony like that could feel.” His blush got even cuter. “Especially you.”

Shining blushed too. He kept rubbing Dusk’s shaft, his hips pumping steadily as he jerked his brother off. He could only make it around halfway down without losing his balance, but from the little moans that kept escaping Dusk’s throat, he could tell it was having an effect.

“I...guess you’d believe me if I said the same to you?” Shining said. “Making you feel good, that is. It just feels...really nice.” He bit his lip, then broke out into chuckles. “Especially now that there’s so much of you to make feel good.”

“Hehe.” Dusk grinned down at him. “You’re really doing a good job. Seriously, I—” He stopped, his eyes flying wide open. “Ooooh.”

Dusk let out a bizarre, low-pitched moan. Shining felt his brother’s body tremble, his cock throbbing as Shining’s length slid against it. “Oh, geeze,” Shining said, panting. "Dusk, you're so...warm."

"Mmff." Dusk closed his eyes, then shuddered when Shining pumped his hips forward. Shining kept going, humping his "bigger" brother's cock for all he was worth. “Oh—oh—yes.” Dusk’s whole face was red, his cheeks puffy with arousal. “Keep going—keep going.”

Shining had little choice—he was set to a rhythm, each hump of Dusk's massive flare in time with his heartbeat. His balls slapped heavily against Dusk’s flare, already refilling with cum. Shining couldn’t remember the last time he’d cum three times in a day—let alone this frequently—but this insane sort of pleasure couldn’t help but turn him on further.

He wasn’t in control anymore. Dusk was in complete control—or rather, his stallionhood and mounting arousal were. “Oh,” Dusk moaned, panting, his big legs quivering. “Oh, Shining. I’m almost there. I’m almost there. I’m almost—ngargh!”

Shining was blasted back, a torrent of cum erupting from Dusk’s slit and violently pushing him back. Dusk just kept moaning happily, bellowing with total pleasure as the force of his orgasm drove Shining to his knees, each gallon-sized spurt of spunk splattering against his “little” brother’s chest. In no time at all, Shining, and the rest of the room around him, had been completely covered by Dusk’s hot cream. He could hear Dusk’s balls churning, sloshing as they expelled more and more of their seed, could feel the floor trembling as Dusk’s moans and squirming made the whole room shake.

When he came out of it, Dusk was breathing heavily. His messy mane was matted with sweat, draping over one eye. “Ooh,” he groaned, his eyes fluttering shut. “Ooh. Yes, yes. It feels so good. Ooh—yes!”

And he began to grow.

Chapter Four: Differences of Size

Shining Armor stared, wide-eyed, as his brother began to expand before his very eyes. Before this, all he’d seen was the evidence, the aftereffects of Dusk’s burgeoning height. But now, the transformation was occurring right in front of him.

Dusk’s head pushed up against the wall, the plaster cracking as he leaned his increasing weight against it. His legs lengthened, going from long to huge, his thighs thickening with bulging, corded muscle as they pushed his hooves across the room. His hoof bumped against the foot of Shining’s Armor’s bed and then kept going. His massive leg slid under the mattress before upending the entire piece of furniture. The poor bed found itself pushed off of the ground and then squeezed against the wall by the giant colt's growing hoof.

Shining’s breath quickened in his chest. Dusk was filling up the room—and fast. It seemed like all of the growth of the last few days had decided to stage an all-at-once encore. In what seemed like no time at all, Dusk’s horn was rubbing against the ceiling, his flanks nearly filling the space between Shining’s closet and the far wall. His hooves were almost touching the opposite side of the room.

Dusk’s scent, his heavy, overwhelming musk, was all Shining could smell. His labored grunts and high-pitched moans were all he could hear. And soon, as Dusk grew and grew and grew, he found that Dusk was all he could see as well, a swelling mass of purple that was coming to fill every cubic inch of space Shining’s room could offer.

And his cock—Shining blinked lazily up at it as it swelled with the rest of him, then yelped as Dusk’s stallionhood began to grow towards him. Its expanding underside rubbed against the rough carpet, further stimulating his giant little brother as it grew. The sensation only seemed to push Dusk to further heights, not to mention what it did to his arousal. Shining found himself pressed against the wall, with nowhere to go—then let out an oof as he felt Dusk’s cock slipping under him. The now pony-sized flare had pushed half of him up into the air, pinning the other half against the wall.

Shining’s ears twitched, picking up a new sound. Was Dusk...whimpering?

“Shining,” Dusk mumbled. “Oh, Shining it’s so hard—I just came and it’s still so hard. What do I do?”

Shining was just barely able to peek over the top of Dusk’s massive flare at his face. When he saw Dusk’s face, he paled. Dusk’s pupils were dilated, more sweat beading on his forehead as his chest heaved up and down. His brother’s head alone was more than half as big as he was; every time Dusk so much as twitched, the entire house groaned beneath the weight of his growing body.

“I—it’s okay,” Shining assured him. Crap, crap, crap. He didn’t think that Dusk would get this big. Sexy fun was one thing, even if it was with his brother. Bringing down the house was another thing entirely. “It’ll be fine, Dusk. Just—don’t do anything rash, okay?”

Dusk didn’t seem to hear him. “Shining,” he whined. He shifted his torso; his head scraped along the ceiling, his hooves pushing out against the walls. Huge cracks spiderwebbed across the room, the ceiling almost cracking beneath the force of his massive horn. His tongue hanging out of his mouth, Dusk panted, “Shining, I can’t reach. It’s just so big and your room is so small.”

“It’s okay,” Shining said again. More and more pre was pouring out of Dusk’s cock, splattering against his stomach and leaving him completely wet. He did his best to rub Dusk’s flare a bit; he could barely even reach his hooves all the way around the head, but Dusk moaned when Shining’s tiny hooves made contact all the same. It was more than a bit awkward trying to jerk his giant brother off while he himself was pinned against the wall by Dusk’s dick, but Shining gave it his best effort.

But it wasn’t enough. Dusk’s shaft flared even wider, a massive glob of his salty precum bursting all over Shining’s belly. “It’s not enough,” Dusk panted, his eyes wide. “It’s not enough. I need—I need—I need.”

He glanced down at Shining, and his pupils contracted. When next he spoke, it was almost like a whisper.

“—You,” Dusk mumbled.

Shining did his best to grin up at him. He kept rubbing, humping Dusk’s flare. All the same, he was getting a bad feeling about the look in Dusk’s eyes. “You’ve got me, right? I’m doing all I can.”

“No,” Dusk mumbled. “I need—I need you. I need to be inside you.”

Shining’s eyes shot wide open. “Uh, buddy?” he said. “Dusk? I don’t think that’s going to work. I really don’t think that’s going to work at all.”

“S’okay,” Dusk said. He seemed to be in a trance. He swallowed, his horn beginning to glimmer brilliantly as eddies of magical power swirled around it. “I—I know a spell.”

“Dusk,” Shining said. But by then it was too late. Dusk’s magic had already picked him up, sliding out from behind his enormous shaft. He dangled before his giant brother, who was panting steadily. “Think about this.”

“Really!” Dusk said. His eyes were wild. “I—it won’t hurt. At all. I’ve tried it before, honest.”

Shining eyed Dusk’s enormous tool skeptically. He’d tried some...kinkier things with Cadance before, but never anything as big as that. It was wider than he was! What Dusk was proposing was nothing short of impossible!

And yet...he had faith in Dusk’s magic, if nothing else. And his brother really did look desperate. His stallionhood was all but gushing pre, a puddle the size of Shining’s bed spreading across the carpet as the floor creaked and groaned beneath Dusk’s pony-sized nuts. And he had to admit...pondering the size of the things that his once-innocent little brother may have taken with this “spell” of his was beginning to turn him on even more. Swallowing, Shining glanced down at Dusk’s shaft one final time before making up his mind.

“O-okay,” he said, somewhat shakily. He licked his lips, feeling his own erection throb. How could that still not have gone away? “But if it starts to hurt—”

“I’ll stop,” Dusk said. “Immediately.” He nodded, and for a moment the overpowering lust left his eyes. But then the lucidity, the sobriety flickered, and his pupils were dilated with need and arousal once more.

Shining considered that. “Okay,” he finally said. “Just—bwuh!”

The glow around Dusk’s horn intensified in magnitude for a second. Shining found himself abruptly turning, spinning with his head over his hooves, as Dusk telekinetically moved him into place. Then sparks started shooting from Dusk’s horn.

Shining’s eyes widened. He glanced down between his legs, wanting to squirm, wanting to feel what was going on down there, but Dusk’s magic held him tightly in place.

Something warm brushed against his flank, and he almost moaned. Dusk’s magic was so...warm, so intimate, brushing against his every hidden place. Then his eyes snapped back open when he felt Dusk’s magic entering him. He felt his legs go slack, his hooves trembling as a strange warmth spread through his lower body.

“Did—did you cast it?” Shining slurred. “Are you ready?” He felt lost in a sea of arousal, his other thoughts muffled by the strength of Dusk’s presence. Dusk didn’t reply at first, opting instead of just push his “little” brother through the air until he was just over the head of his cock.

Shining eyed the throbbing, massive cock with no small amount of trepidation. Suddenly, he was a bit unsure about the whole thing. “Are—are you sure that it’ll fit?”

“It will.” Dusk grunted again. Shining watched as a fat glob of pre the size of his head bubbled from his brother’s tip, splattering all over the floor. “I promise.”

At least he sounded earnest.

Shining took a deep breath. “Okay,” he said, steadying himself. He had to trust Dusk. He wanted to help Dusk feel good. And, deep down, he had to admit that the idea of fitting something that huge inside of him—something that huge, and belonging to his brother—was one of the hottest things he’d ever conceived of. “You can put it in now.”

Dusk levitated him down, and thrust his shaft upward. When Shining felt his brother’s enormous rod prodding hopefully against his tight, muscular flanks, a thought occurred to him: Dusk would be less putting it in Shining than putting Shining on himself.

And then Dusk started pushing, and Shining started howling.

It wasn’t that he was in pain—some part of him had expected to be, magic or no, but Dusk’s spell had done its work. He felt nothing at first, save for the most bizarre sensation of stretching. His stallionhood was throbbing harder than before, which contributed partially; the sensation was both incredibly alien and incredibly erotic. Shining squirmed, panting, his chest heaving as he felt Dusk spreading him wide around his flare.

Dusk stopped immediately. A tremor returned to his voice, a flicker of lucidity. “Sh-shining?” he stammered. “Should I stop?”

Shining inhaled deeply, his mane matted with sweat. “No,” he gasped. “It feels—it feels good. Keep going.” He felt Dusk twitch inside of him—or rather, twitch his whole lower body, his brother’s massive flare setting his whole body squirming with each thrum of blood through its length.

“Okay,” Dusk said. “Just—tell me if you want me to stop.”

Shining took another breath. Then, feeling his brother’s magical grip on him loosen, he turned back to face him. Shining was grinning like a madpony.

“Don’t stop until it’s all the way in,” he said. “You hear me?”

“Shining—”

“What are you waiting for?” Shining hollered. “Shove it in!”

And Dusk did.

Shining howled even louder, his brother’s girth stretching him impossible amounts. It’d been ludicrous—insane—to think that a cock the width of his entire torso could fit into his ass, but somehow Dusk was managing it. Shining writhed, wailing, grunting, and wheezing in pleasure as inch after inch, then foot after foot of Dusk’s stallionhood entered him.

Soon enough, Shining saw something poking up on the bottom edge of his vision. Glancing down, he saw his stomach actually beginning to bulge out. A full foot of Dusk’s length slipped inside of Shining’s ass, and both brothers moaned together. Shining had both his hooves on his stomach, massaging it, feeling the curve of Dusk’s gigantic flare beneath his coat.

“Nngh,” Dusk groaned. “You’re so tight.”

Shining nearly choked. “Says the stallion using me as a cocksock.”

Shining could barely even turn his head at this point—the bulge in his belly had to be a good foot tall by now—but he could imagine the exhausted grin on his brother’s face when Dusk replied, “Yeah, but you like that.”

“And you don’t like me tight?” Shining clenched his flanks a few times, flexing his cheeks around Dusk’s massive girth. It didn’t do much, considering Dusk’s sheer size, but it was the thought that counted. Instantly, Dusk groaned, the churning in his balls actually becoming audible as a huge geyser of precum burst inside of Shining’s stomach. Shining grunted, his hooves pressing into his middle as he felt it bloat outward with the sheer volume that Dusk was pumping into him. He wasn’t even cumming yet.

Dusk just pushing himself in. It felt like his shaft would never end—and Shining never wanted it to end, besides. He goggled when he saw the bulge in his stomach pushing far above him. He grunted, pressing around his middle as he felt his stomach softening around the sides of Dusk’s shaft. It was plumping up with what had to be bucketfuls of pre. Shining gasped for air, coughing as he felt his once-little brother turn him—his entire body—into nothing more than a covering for his cock.

And he loved it. He’d never been harder in his life.

“I love you tight,” Dusk corrected him, grunting between every word. He thrust his hips forward, at least as much as he dared without shattering the floor beneath his weight. “I love feeling how big I am inside you. Oh, gosh, Shining, I can see my shaft inside you.”

Shining grunted, squinting up at the monstrous shaft poking up above—up through—him. He patted it, then moaned, his whole body spasming as Dusk pumped his hips a few inches forward. “That you can, lil’ bro,” he mumbled, feeling his belly squish as more and more precum gushed into him. “That you can.”

The room was too cramped—or Dusk too big—for Shining to actually received a proper rutting. So, instead, Dusk merely took hold of him with his magic and began to pump Shining’s smaller body up and down his shaft, squeezing him around his girth.

Was it him, or did Dusk feel a little...bigger inside of him than he had a second ago? Shining glanced down. He could actually see Dusk’s hooves stretching across the floor, could hear his head scraping against the ceiling as he grew to fill it even more completely. Dusk was growing around him, beneath him, inside of him. He wasn’t anywhere near done growing—not even close.

Shining moaned, his own erection spurting a generous—for him—amount of precum down onto the floor. “Oh, fuck,” he moaned, squirming as Dusk filled him up. “Oh, fuck.” He loved this feeling: being taken, being used. He was nothing more than a toy to cover Dusk’s cock so that his massive little brother could pleasure himself. He’d never been more turned on in his life.

Dusk was panting harder now. The amount of pre pouring into Shining redoubled in volume, rounding out his belly considerably. “Shining,” he gasped. “I’m gonna—I’m gonna cum.”

“Do it,” Shining gasped, his voice hoarse. “Dusk, I want you to cum inside me. I want you to blow your load inside me until I can’t even walk. I want you to fill me up with your damned giant orgasm, every last damn drop.”

That was all it took to set Dusk off.

Shining’s eyes bulged as Dusk’s flare swelled impossibly wide inside of him. He howled, stretched past even his previous limit, and moaned in absolute pleasure as the first flood of Dusk’s seed gushed into him. The first spurt alone outmatched his entire production of pre before; soon, Shining found himself moaning even louder as Dusk’s monstrous orgasm filled him past any reasonable fantasy.

It came flooding into him, each contraction of Dusk’s shaft forcing Shining further down, filling him up and stretching him until he could barely move. Dusk was crying out, his massive balls pumping a veritable ocean of cum into Shining’s gut. Shining kept howling, beating his back hooves against Dusk’s enormous member as it filled him to bursting.

Warm, hot spunk filled his belly, each new bulge of jizz stretching his ass even wider than it had been before. Before long, the amount of cum inside of him had stretched his stomach enough to compete with Dusk’s cock in size; just two massive spurts later, and Shining’s stomach was an enormous, round sphere full of cum.

He coughed, then blinked. He tasted jizz on his tongue—and not just any seed, but Dusk’s seed. But how was that possible? He hadn’t given him a blowjob. He’d never even—

Dusk’s stallionhood erupted inside of him again and Shining coughed up a fat wad of Dusk’s cum. It landed on his belly, splattering against his coat, and matting the fur there even further with Dusk’s hot, sticky load.

He’d never felt so full. Even with Dusk filling him, there had still been some element of individuality, of separation. But now, with Dusk’s spunk ballooning his belly out, Shining was having trouble even seeing himself as something separate from his brother’s orgasm. He was filled, every inch, every drop, with his brother’s seed.

It was almost too much, though. Shining’s gut was stretched wide, impossibly wide, by Dusk’s load. He could feel his belly churning, sloshing as it expanded far beyond any rational size. He felt so tight, the skin over his gut pulled so taut as it struggled to hold in its colossal meal. He felt like he was about ready to burst, as though Dusk’s cum was just too much for him to hold inside of him.

Two things immediately happened. One: Dusk’s cock bulged even wider inside of Shining’s rear. Two: Dusk finally broke through the roof of the house.

It was hard to say which happened first—to both stallions, the entire scene was just a blur of overwhelming pleasure. All Shining Armor knew, though, was that one moment he had been speared on the end of Dusk’s flare, and the next, he was shooting through the air, exploding off of Dusk as the pressure inside of him finally became too much to allow any more cum to enter.

But he didn’t hit the ceiling. He didn’t hit the roof, either. Dusk was too busy growing right throw it. The giant stallion’s moans redoubled as the ceiling crumbled around his burgeoning body. The abused plaster finally cracked, his head shooting right up past the second floor ceiling and up through the attic. Dusk gasped as his head exploded above the roof of the house, greedily gulping down huge amounts of fresh air.

All that size, all that weight, all that growth proved too much for their poor house. It may not have been one of the more fragile apartment buildings of Lower Canterlot, but even the Velvet household could only stand so much abuse. Dusk’s now several-ton weight collapsed the floor to Shining’s room; within seconds, much of the first floor was debris beneath his huge, expanding ass.

Dusk just kept moaning, shooting huge amounts of jizz up into the sky, which then splattered down over the wreckage and street before him. His hooves stretched down until they reached the sidewalk, every shift of his colossal body sending the ground shaking. Each spurt of Dusk’s orgasm sent hundreds of gallons of hot stallion cum splattering all over the street, covering it in a thick, sticky, musky white.

Shining flew through the air, his hooves waggling wildly and smacking against his huge, bloated belly. His mind was still awash in pleasure and shock, so much so that he barely even noticed when he hit the ground.

His massive belly spread out below him, a cushion that prevented any real damage. All the same, the impact set his whole body jiggling, his cum-filled gut sloshing from side to side as he moaned.

His vision swam before him. Shining groaned, blinking rapidly as he struggled to recover. Without Dusk plugging him up, a waterfall of cum poured out of his gaping asshole. Shining gritted his teeth and clenched his flanks. He could feel his hole slowly closing, slowly but surely returning to its normal radius. All the same, he still felt hugely loose. He had no doubts that he’d be walking funnily for the next few days. By now, his ass had only managed to close to around half of its maximum size, but enough of Dusk’s penetrating force lingered to keep it nice and wide as a river of hot, giant stallion jizz poured out onto the ground below.

The ground… As Shining’s belly slowly deflated, he let out another moan, his eyes fluttering open. The first thing he noticed was the odd color of the ground. It wasn’t the grass of the front lawn. Nor was it the red-and-white tiling of the street, or the cement of the sidewalk.

For some reason, the ground was...purple?

Shining blinked down at the surface he’d been resting on. Then he realized that he could still smell Dusk’s musk—stronger than ever, in fact.

He wasn’t on the ground—he was on Dusk. The “floor” below him was a vast, purple-furred sphere that only felt flat because of how large it was. Shining gaped as he slowly glanced up. His cum-filled belly squished slightly against the plump surface of what could only be Dusk’s equally cum-filled orbs. Soon enough, the rest of Dusk’s body came into view.

He was massive. He towered above the wreckage, his horn poking up above the nearest rooftop. Each one of his balls would have likely been close to dragging on the ground had he been walking; his shaft, which towered far above his head, was the biggest that Shining had ever seen, both absolutely and proportionately.

Dusk was leaning back, his forehooves crushing a pile of debris behind him. His chest heaved as he panted. Sweat poured down his forehead; every few seconds, the enormous shaft before him throbbed hugely, and he cried out before biting back down, whimpering. A steady river—and this time, it really was a river—poured down the side of his member, pooling between his balls before leaking down onto the grass below.

With a start, Shining realized that he’d just seen Dusk surge up again in size. His brother was nearly four stories tall, and he was still growing. Glancing back over his shoulder, he saw Dusk’s back hooves stretching toward the Canterlot road, his legs lengthening by the second.

Dusk appeared paralyzed with pleasure. He had both his eyes closed, and was panting madly. “Ooh, yes,” he moaned. “Growing feels so good. Gotta...get huge. Get so big. Get bigger and bigger and bigger.”

“Dusk?” Shining tried to pull himself to his hooves and just barely managed. His belly, though still round and taut from the amount of cum Dusk had pumped into him, was a bit more manageable now. At least it didn’t stretch past his knees, so he could still stand. “Dusk, you’ve got to try and stop growing! You’re getting too big!”

And he was. A hoofball-sized Dusk had been one thing, and a “tallest pony in Equestria” award would have been fine. Even a room-sized Dusk would have been okay, though he would have had a hell of a time fitting anywhere but the Palace from then on. But now...Dusk was getting way too big. Soon enough, he’d swallow up the entire street—and where might he stop after that?

One of Dusk’s eyes peeked open; for a second, he seemed to notice Shining. Then his monstrous cock throbbed again, and his eyes squeezed shut. His whole body shuddered. Sparks shot from his horn, and a visible purple aura pulsed around his body as his growth redoubled. “S-so hard,” Dusk panted. “Oh, this feels so good.”

“Dusk!” Shining hollered. “You’ve got to stop! You’ve got to—” He shut himself up. It was clear that Dusk wasn’t listening. He had to get his attention, or else find some other way to stop him.

Then his “little” brother’s dick throbbed again, and Shining had an idea.

Dusk’s moans echoed through the neighborhood. He was swaying lightly, his massive shadow falling over the houses below. More and more ponies were lining up on the street, gaping, as his gigantic form grew to swallow up the wreckage of the house.

And then he faltered. His moans paused—and then redoubled when he felt a pair of tiny hooves wrapping around his shaft.

Shining had his hooves stretched as wide as he could, and they still weren’t anywhere near wide enough to hold a meaningful fraction of his brother’s cock. Still, he couldn’t deny that the very act of pressing his body against his “little” brother’s stallionhood turned him on than anything they’d done before. Dusk’s giant slab of meat was pressed right up against his face, his chest, and his crotch, his growing brother’s shaft rubbing against every inch of his body.

Dusk groaned, his eyes fluttering just the tiniest bit open as Shining pleasured him with his entire body. Their incredible size difference was clearly turning him on, driving him further toward the edge. That was just what Shining wanted.

“Sh-shining,” Dusk groaned. His voice boomed out across the neighborhood. “Shining, I’m so big.”

“Yes,” Shining mumbled. He doubted Dusk could even hear him like this, given how much noise Dusk's  giant body was making, and how tiny he was by comparison. “Yes, you are.” He redoubled his efforts, humping Dusk’s shaft as hard as he could.

“So,” Dusk mumbled, “so, so big.” Everypony in the neighborhood could see him now: his huge, swelling body, splattered with enough cum to fill a small lake, muscles swelling and rippling beneath his coat. “Oh, Shining, I’m just so huge.”

A glob of pre, as wide across as a wagon, burst from his tip. It landed somewhere on the street, right among the gathering crowd. Several ponies shrieked and dodged away. But Dusk didn’t seem to care. He went right on panting, went right on growing, still stroking the tip of his shaft as Shining humped the bottom.

“Yes, you are,” Shining said, almost in a whisper. He closed his eyes, imagining. The rush that Dusk must be feeling—the allure, the pleasure of ever-increasing size—must be...intoxicating. The euphoria that must be filling his every muscle, the duel between reason and lust as his libido grew to unbridled heights—even imagining it was incredible.

Dusk’s eyes may have been closed, but Shining could tell that his once-shy brother was revelling in the attention of the gathering crowd. The feeling of strength, of absolute dominance his enormous body created, was almost stifling. Shining took a deep breath, filling his lungs with Dusk’s intoxicating scent as he humped his brother’s house-sized length again and again.

To be so big—Shining wanted it so badly. To feel yourself expanding, swelling, outgrowing everything and everyone you had known before. To throw out your limbs farther and farther every morning, to see the ceiling getting ever-closer—and then, once you’d outgrown the ceiling, the very sky itself. Shining wheezed, gasping as arousal pulsed through his veins, Dusk’s all-encompassing lust for size pumping through his veins.

“I wonder—” Dusk gasped, surging up in size and losing control for a moment. His titanic cock throbbed, soaring above the houses below. “—I wonder—mmff—how big I’ll get, Shining.”

Oh, Shining had an idea of where this was going.

“Bigger—nggh—than you,” Dusk said, panting. “Bigger than the house. Maybe bigger than—ooh, yes—Canterlot. And maybe—I’ll be strong enough—to get bigger than all of Equestria.” He shuddered, his whole body going erect with dreams of size. And his stallionhood trembled.

It was clear how much his fantasizing was turning him on. The river of pre down his length doubled in width, becoming a warm, thick flood of lust running down his meaty shaft. Shining joined him in his fantasies, squeezing his eyes shut as he rubbed his whole body along Dusk’s length, dreaming of being big.

Big. Huge. Enormous. Gargantuan. Towering over other ponies—over rooftops—over entire cities, always growing, never stopping, always lusting for more and more and more—

Shining bit down on his lip, squeezing his eyes even more tightly shut as a wave of arousal shuddered through him. With his eyes closed, though, he didn’t notice when the shimmering purple magic around Dusk’s body flickered—then spread to cover him, too.

Shining had only been slightly wrong before. Though his hooves and body were mostly far too small to please Dusk effectively, the simple fact that his once-big brother had been reduced to using his whole body to jerk him off had turned Dusk on like nothing else. To feel Shining’s whole body against his base—to know that other ponies were almost like mice, or like insects to him now—drove his arousal to new heights. Dusk had never been a mocking or elitist stallion, but the feelings dominating his body right now threatened to overrun everything else.

Yet Shining wasn’t quite so small anymore. Dusk’s magic was flaring, burning around him, the sheer energy of the giant colt’s magic actually evaporating off of his fur—and leaping into the nearest available host. Shining shuddered, his whole body going erect as Dusk’s magic flared inside of his chest. At first he felt dizzy; then, he felt a tingling dancing up and down his spine. A feeling of aroused bliss was spreading throughout him, a physical euphoria greater than the most powerful aphrodisiac.

And he was growing. Not as much as Dusk—nowhere close, really—but with each breath Shining took, his body swelled a little bit upward, a little bit outward. At first it was just an inch, then two, then four—every hump, every grind against Dusk’s magnificent shaft bringing new size to Shining’s growing body.

Dusk’s shaft was still far too wide for even him to fit both hooves around it, but Shining was growing fast enough that, suddenly, just hugging it didn’t seem so impossible. Dusk’s eyes fluttered open, his breath catching, as he felt the “insect” rubbing against his meat suddenly become a chipmunk—and then a squirrel. Shining was growing, and the bigger he got, the more he could pleasure his also-growing brother.

By now, Dusk was nearly forty feet tall, just sitting down. So much precum had streamed down his dick that he’d drenched Shining in it entirely, covering him and the entire surrounding area with a thin, milky-white finish. Shining gritted his teeth, only partially conscious of his swelling body—he was more than seven feet tall now, had he been keeping track—and just grinded his body even harder against Dusk’s.

Something was rumbling beneath Shining’s hooves: Dusk’s balls, a pair of massive, cum-laden nuts huge enough to reach nearly halfway up his stomach. Dusk was wheezing, gasping for air as his massive body reached a level of peak arousal. Shining just clenched his teeth, humping even harder as he felt himself approaching his own peak. He wanted to cum with Dusk—needed to cum with him. He no longer cared about stopping him; he just wanted to see his brother grow bigger and bigger until there was nothing else left to outgrow—

Dusk’s hips were jerking, slamming onto the ground every time he pumped his shaft beneath his hoof. Each slap of his flank against the ground caused a miniature earthquake; his massive, several-ton body was absolutely enormous. Shining didn’t even care. So what if it was a little hard to hold on? He needed this—needed to feel Dusk’s stallionhood against every inch of his body, rubbing himself against it, covering himself in his once-little brother’s musk as he ascended to unfathomable heights.

By the time Shining had reached nearly one and a half times his original size, Dusk was approaching fifty feet. With so much size, so much growth, so much lust roaring through both stallions’ systems, there was only one place for all that arousal to go.

Out.

The rumbling reached its peak—then paused. A mighty, terrible shudder echoed through the earth.

Then Dusk’s orgasm exploded.

A tidal wave of spooge burst from his tip, his shaft flexing hugely as it erupted with cum. Dusk’s massive, spongy head puffed up, bulging as a flood of cum burst from its depths. Gobs of spunk, each one bigger than a full-grown stallion, rolled down his length and nuts. Dusk’s moans reached a roaring crescendo, his whole body twisting and jerking as he rapidly pumped his massive shaft.

Shining came with him, crying out in overwhelming pleasure as he felt Dusk’s girth lurch and shudder against his chest. There was no doubting how much Dusk had needed this—how much he’d needed to cum, struggling to keep his titanic load down against an overwhelming urge to find release. And now, in this moment, Shining found release with him.

Cum kept erupting from Dusk’s flare like from a volcano. Huge globs of thick, creamy white cream splattered the nearby rooftops, painting the town white. Shining couldn’t imagine how incredibly, impossibly full his brother had been, how painfully pent-up his growing size had made him feel—and how good it must feel now to drench the neighborhood in his jizz.

He moaned, rubbing against Dusk’s shuddering shaft as thick gooey spurts of his own cum painted Dusk’s girth white. Dusk’s prodigious amounts of spooge were actually pooling into ponds and lakes around the lawn and on his own massive ballsack; a swelling pool of jizz, hot, musky, and creamy was lapping at Shining’s hooves, staining his fetlocks a thick creamy white. Each lurch of Dusk’s cock brought another ton of jizz arching through the air before it crashed down on the pedestrians below, bathing the street in his spunk.

Jets of Dusk’s giant-sized orgasm spattered noisily against the road and buildings alike. He gasped, his whole body shuddering with pleasure as he fired shot after thick, gooey shot into the air. Shining was writhing against his brother’s length, overcome with pleasure as he was absolutely drenched in his brother’s cream. It just kept coming: a torrent of cum, a cascade of spunk so thick and virile that it seemed endless, even as Dusk’s orgasm tried to drain every last ounce of cum from his nuts.

And then, finally, it was over. Dusk gave a final moan as his cock gave one last throb—then flopped back onto the yard below. He groaned, his hooves digging out deep gouges into the ground. Shining gasped as he found his anchor—Dusk’s titanic shaft—bending forward over his brother’s torso. Then he yelped, losing his balance and tumbling hooves-over-head until he came to a rest on top of Dusk’s cum-splattered belly.

Shining groaned. His head was spinning, and he felt sore all over. Rubbing his horn, he grimaced, then slowly raised his head—to see Dusk grinning down at him.

Dusk may have been lying down, but his head was still so much bigger than Shining that he had to look down to meet his eyes. Still, Shining could easily see the bright light dancing behind his brother’s eyes—not the flaring, lust-driven gaze he’d had before, but the intelligent spark he’d always known his brother to have.

It looked like Dusk was back in control.

He was blushing hugely, though his smile stretched from ear to ear. “Wow,” Dusk said. “That was...uh, something.”

“You can say that again,” Shining said. It was still sinking in just how big Dusk was compared to him, but at least he didn’t seem to be growing anymore. Though for some reason, Dusk seemed a bit...less huge than before. Huh. He blinked rapidly, feeling lucidity returning to his thoughts.

Dusk grinned sheepishly. “I, uh, saw what you were doing down there. That was really hot.”

“Oh.” Now Shining was blushing, too. “Glad you liked it. Heat of the moment, I guess.”

“Mmff.” Dusk peered down at him, blinking with a pair of pony-sized eyes. “Huh. You look a little...bigger than you did before.”

“Maybe you just shrunk?” Shining offered. Then again, he noted, glancing around at the other houses, there was little chance of that happening.

Dusk chuckled. “Don’t think so. But you do look different.”

Shining glanced down at himself. Then he glanced at the crowd of ponies down in the street. Funnily enough, they did look a bit smaller—and it wasn’t just because he was perched on Dusk’s chest. “Wait. You think—”

“That some of my growth spread to you?” Dusk beamed down at him. “Maybe.”

Shining opened his mouth to reply, then grunted as a sudden weight swept him to his knees. Squinting to his side, he saw Dusk’s hoof, which wasn’t quite bigger than he was anymore, pressing him down. Then he realized: Dusk was hugging him. Or at least as much as any fifty-foot tall giant could hug a much smaller pony.

Dusk laughed softly, hugging Shining to his chest. His oversized hoof wrapped around his brother’s middle, pressing Shining against his cum-stained fur. “Growing feels really good,” he confessed. “But...it didn’t feel half as good without you helping. So thank you. For helping me feel good.”

Shining struggled against the weight of Dusk’s hoof, then decided to give up. Instead, he squirmed himself into a more comfortable position on his brother’s chest before glancing up again. When he did, he noticed that Dusk’s big cheeks were bright rosy red. That was when he realized that his own cheeks were burning as well.

“Um,” Shining said, grinning. “I liked it, really. Making you feel good. And seeing you get so big was just—man, words can’t even describe it.” He snuggled against Dusk’s chest, pulling his brother’s hoof closer around his middle. Dusk looked surprised for a second, then smiled drowsily.

“Mm.” Dusk’s eyes fluttered a bit. He began to massage Shining’s back gently, his touch surprisingly light for how heavy his hoof was. “Shining…”

“Mmhm?”

“Would you want to be big too?”

Shining yawned. The afterglow of his cumulative orgasms was spreading throughout his body, making his every muscle feel lethargic. “Mm. You bet I would.”

“Mm.” Dusk began to rock his big body back and forth, still rubbing Shining’s body. “Maybe we can...find a way to make you as big as me, then. A growth spell or something.”

“Really?”

“Mmhm.” Dusk’s smile softened. “Dusk ‘n Shining. Biggest stallions in Equestria.”

“Heh.” Shining snuggled further into Dusk’s chest. “I think I’d like that.”