“You know about that?”

“BPC, everypony at school knows about that,” Cookie smirked — her eyes pulling off of her big brother’s tool with reticence. “It was like I was a minor celebrity today — every filly asking me if I was really the sister of the BPC.”

Caisson groaned, one of his forehooves coming up to massage his head. “Great, so now my little sister knows I’m the laughingstock of the of the whole school.”

“Laughingstock?” Cookie incredulously clicked her tongue and raised an eyebrow. “You kidding me? Try hero-hearthrob.”

“What?”

“Every filly from every grade was chatting me up all day today!” Cookie grinned, her tail flicking back and forth as she affected a falsetto tone in mimicry. “‘What’s your brother like?’ ‘Has he always been so big?’ ‘Have you ever walked in on him when he’s hoofing himself?’ ‘How can I get a date with him?’ ‘Why won’t he ever chat with me in the halls?’”

“Uh…”

“Seriously, even Principal Cheerilee told me I had to keep an eye out for you: ‘You’ll need to keep a close eye on him, Cookie. This town hasn’t had a colt like your brother since Big Mac… and even a lot of mares around town prefer the color pink to Mac’s black.” Cookie snarled her lips and clicked her tongue. “As if I didn’t realise she was talking about scoring you for herself.”

“I, I really think you’ve got it wrong Cookie.” Caisson gulped, ears folded back. “I haven’t even spoken with a filly, let alone had a date with one. A girl wouldn’t be caught dead with a big, gross, lunk like me… even before they saw this, this thing between my legs.” He shuffled his hind leg with frustration, spitting the word with venom. Why was he cursed with this body?

“Uh huh.” Cookie deadpanned, staring at him. “I’m starting to think maybe you aren’t so good at reading a filly, big bro.” She chuckled, her tail flicking a little bit higher.

“I know I’m not.” Caisson groaned. “Just one more thing that’ll pretty much guarantee your brother will end up a kissless bachelor who’s good for nothing put plowing.”

“Pft.” Cookie rolled her eyes at him before quickly snapping her attention back to underneath his barrel. As her pupils widened once again as they fixed upon his shame, Caisson swore he could see her chew her lip as her tail hiked ever so slightly upward. “Well, after hearing from basically every filly and half the mares around school today, I’m sure you’re going to get very good at plowing, BC.”

“E-every filly?” Caisson’s head tilted. His brain was having a little trouble computing what his sister was talking about.

Cookie’s eyebrows knitted together, her nuzzle forming into a bit of a snarl. “I had to bite my tongue most of the day. Seriously, who do half those randy tail-flippers think they are? They don’t know the first thing about my big brother!” She stamped her foot, tail flicking upward in its semi-flagged position. “They’re treating you like some piece of meat and not the wonderful, kind, caring stallion you are! You’d better believe I’m not just gonna let any tramp get near my brother just because he’s some sort of trophy, they’re gonna have to do it proper — treating a stallion like a mare should!”

“Um.” Caisson mumbled, blushing at his little sister’s possessive outburst. “I… I don’t think anyfilly will ever get to know m-”

Cookie clicked her tongue and stamped again. “There you go again, BC. You really don’t understand a filly’s heart. Even with the number of shameless tail-flaggin’ post-grinders asking after you, you can’t just expect a girl to trot up to you and give you a hoofie...”

As she spoke the words, her ears folded back and that strange shiver rolled through her again, like some thought had just sprung into her mind. Caisson watched his little sister’s eyes flick from his stallionhood to his face a couple of times, as she toyed with one of her hooves on the barn floor, pawing idly at the dirt. He watched her, trying to understand just what she was thinking, looking from her hoof to his underbelly, when she suddenly winced and snorted.

“Ummnf!” Cookie squeaked, a red flush washing her face.

Caisson had been focusing on her eyes and hoof, and so he only barely caught the strange shimmering squirt of motion that came unexpectedly from her backside. Again that overpowering stench swamped the air of the barn — it had never felt so stuffy in here, not even during the height of the mid-summer heat.

His stallionhood throbbed, hot blood pressing against its fleshy-pink skin.

“A-anyway…” Cookie quickly chirped, quickly drawing his attention away from her rear. “Time to get your bellyband strapped in, BC.”

“C-cookie…” Caisson began to choke out, his mind scrambling for the words to tell her to stop. The belly-strap would go right across the midpoint of his shaft — harnessing this final piece would bring the young teen directly into contact with his painfully rigid erection. “I-I don’t think…”

“Now this’ll be a bit of a pickle.” Cookie hummed, ignoring him as she stepped in and took hold of one side of the loosely hanging belly-strap. “Seems like you’ve threaded your needle through this loop here.” She grinned, eyes not leaving the area underneath him. “And we can’t buckle your winky-wee underneath the strap that would pinch like a-... what?”

Caisson couldn’t help giggling. “Winky-wee. Haven’t heard you say that for a while. It’s cute.”

Cookie blushed again, blowing a snort out of her nostrils and stamping. “Hey, I’m a big mare now!”

“I know.” Caisson grinned. “‘Winky-wee’ just reminded me of when you were a foal, is all.”

“Cock.” Cookie sniffed, flipping her nose up. “You’ve got a buckin’ huge, mare-splitter of a drippin’ horsecock, BC.”

Hearing those words come out of her mouth was stunning, Caisson swallowed, trying to stifle his reaction. Why was hearing her say that so exciting?

“See? I can sling dirty words just like any of those trashy fillies at school. Hmf.” Cookie swung her head disdainfully. “Now, like I was saying. No way I can buckle you in so long as your cock is, uh, stickin’ up.”

“Can’t we just undo the bellystrap completely from both sides and then —”

“No way, that would shift everything I’ve already set.” Cookie quickly cut him off. It seemed to Caisson her eyes were a bit too spritely, nervously dodging meeting his gaze. “I’d have to start right from scratch, that’d take ages.”

“Uh, I guess.” Caisson hesitantly agreed. “J-just give me a couple minutes to calm down then, and the —”

“I just said we can’t wait any longer, BC.” Cookie huffed, still scrunching her nose and looking away from his eyes. “I don’t want Mom and Dad thinkin’ I’m the cause of you being late out to the fields on the very first day I’m strapping you up.”

“Well, what do you want me to do?” Caisson groaned, exasperated and embarrassed.

“Can’t we… y’know… take care of it?” Cookie finally looked at him as she said it, a blush on her face as she made a slow pumping motion with her right forehoof. “If you hoof one out won’t it go down?”

Hoof off? In front of my sister?

Caisson felt his cock jump and slap against his belly — just why did that excite him?

“I dunno Cookie, I shouldn’t do that in front of you.” Caisson mumbled. He knew he had to say the words, even though he was somewhat interested in doing that in front of her. Something about those big blue eyes, having them watch him… “Maybe if you stepped outside. Kinda weird that you know I hoof mysel —”

“Oh please, like Posey and I don’t hear you grunting and bumping against your wall every other night.” Cookie rolled her eyes. “Gimme a break.”

“O-ok.” Caisson gulped. “I guess I can.”

“Do you need help?”

The question was like a thunderbolt in his ears, clearing all other thoughts out of his mind. The surge of adrenaline made him almost kick a rear leg reflexively.

His sister… helping?

The images were too potent to hold in his mind’s eye, though they burnt into his neurons.

“W-what? N-no, I know how to —” Caisson stumbled with his words.

“I mean,” Cookie started to fumble her words herself, babbling just like she had earlier. The words started to spill from her fast and faster “I’m just thinking you’ve probably never done that in a harness before. Hoofed off I mean. At least, not that I’d seen. Not that I’ve ever seen you hoof off at all. But I just thought, you know, maybe with the straps you might get all chafed, might not be as easy to turn around, and since it’s my job, right, to help you out...”

Her ears were folded back, her face blushed, her eyes misty: it was clear that she had really wanted him to agree.

Caisson blinked, looking at her. She was so adorable, so vulnerable. It was so clear that she wanted with her entire being to do this to him.

For him.

He also knew that it was his duty as a big brother to say no. To stop this train before it left the station.

But there were also her looks. Her beautiful muzzle with its painted stripe, her ruffled fur, her mane and tail, her tight little rump. It screamed to something else in him, an ancient pride — this mare wanted to do that for him.

And that smell.

The thick aroma was like a cloud in his thoughts, as if the very air he was sucking into his nose was filling up his skull, getting in the way of every one of his neurons as they tried to fire.

So, when that moment came for him to say no...

He didn’t.

They stared at each other for a long moment.

“B-BC…” Cookie whispered, looking up at him. Those eyes were so deep, so blue. And there was a fire burning in those dark pools — a raging want.

Caisson felt his cock twitch again, and this time a wet trickle of his own spattered against his own chest fur, dropping in a heavy, sticky strand to the floor below.

Cookie noticed. Her nostrils flared wide and she shut her eyes with a contented hum, like a half-awake pony getting their first whiff of coffee in the morning.

“OK.”

He wasn’t sure if he said it or she did. His mind was in complete shambles. Thoughts of guilt, excitement, and instinct all competed millisecond by millisecond for his headspace — leaving only pure reaction and sensation as the siblings began to cross that forbidden bridge.

He was brought back to the present by the touch of a hoof against his stallionhood, the press of Cookie’s hoof-edge against the very large base of his shaft near to his testicles.

“Neeee-ah!” The whinny escaped him unbidden, his body stiffening and his cock bouncing under him as his pelvic muscles clenched and released. One of his rear legs stomped menacingly.

“Ah, sorry.” The hoof pulled back. “D-did I do something wrong?”

“No! I was just, ah, surprised.”

“Ah.” The hoof came back, quickly.

My sister’s hoof.

On my stallionhood.

His heart thumped hard enough that he thought it was going to pop in his ribcage. A filly was touching him. On purpose.

Cookie’s hoof pushed in harder, bringing the soft under-belly of her frog into contact with his pink heat. She began to rub back and forth, only an inch or so up and down, never straying far from the familiar territory where her touch had started. Uncertain, inexperienced.

Amazing.

“H-how’s that…?” Cookie breathed as much as spoke, curiously looking at him, hungry for feedback.

“Mm… C-cookie,” Caisson groaned. There was an element of embarrassment to this, sure. A sibling giving you an awkward hoofie in the barn, somepony he was so close to suddenly entangling with him in such an intimate way. But it was quickly being overtaken by a feeling of pleasure. “H-higher…”

It was all he could manage without devolving into a blushing, guilty mess.

“L-like this?” Cookie started to rub along his shaft closer to where the sheath connected to his belly, the top of his stallionhood — the dorsal surface.

“N-no… up.” Caisson gulped, letting out a soft breath as he accepted the sin, the wrongness of what they were doing. “Up. Near the tip.”

“Oh.”

The hoof began to trace its way up his rigid log, never leaving its surface as it slid, inch by inch, over his pink girthy base, up to his medial ring.

“B-buck.” Cookie whispered, just as her hoof slid over that muscular ring of flesh.

“What?”

“Just…” Cookie nervously replied, her ears flicking over to him, as she realized her invective outburst had been caught. “Y-you’re… just so b-buckin’ big.”

Caisson felt her lean some of her weight against his barrel for balance as she lifted a second hoof off the ground. With this new hoof available for use, she pressed against his shaft, on the opposite side of where Cookie’s original pleasure-paw had paused on his medial ring. “I can’t even wrap two hooves all the way around at the ring.”

A grasping squeeze of her hoof confirmed her observation, neither of the filly’s hooftips managing to touch around his huge erection, even at the midway point. The sensation of constraint brought another rumbling nicker through Caisson’s belly. He felt the sensation of squeezing pressure in his sack, his muscles pushing against his prostate. The twisting tightness inside his heavy balls from his swollen epididymis was brutal: he had never felt so full.

The ripple raced up through his stallionhood, erupting from his tip in a heavy splatter of clear pre-ejaculate. He’d never had pre-cum like that. In such abundance.

“Sorry.” Caisson groaned.

“You better stop apologizing for being so well-hung, BC.” Cookie giggled, sticking her tongue out at him — a reprieve from the anxious sanctity of their whispered silence. “It’s like saying ‘sorry for being so awesome’.”

“I was, uh, apologizing for…” Caisson blushed, embarrassed. “Dripping.”

“Oh?” Cookie slid her hoof all the way up to the orifice in question, running the delicate pad of her left hoof right over Caisson’s glans and smearing the clear fluid in question all over her hoof.

Caisson groaned. The explosion of sensation was too much for such a tender and erogenous bundle of nerves to handle such direct stimulation. He felt his left rear leg lift a few inches off the ground, kicking out slightly.

“I don’t mind — it smells amazing.” Cookie didn’t notice, still rubbing his stallionhood’s head. “Your drippings, I mean.”

She would have plenty to explore on him.

His bulbous end was as wide across as a saucer-plate, a huge crown topographically adorned with two prominent mound-sized protuberances, all separated by a milkshake-straw-sized urethra right in the lower center.

A stallionhead.

His little sister’s hoof was soon wet with the sticky-slick dribble that effused from him, as she swirled in circles that went wider and wider… until she was massaging the nubby bumps of the edges of his glans — which were quickly throbbing to a painfully engorged state.

“Oh. Oh…” Caisson groaned. “C-cookie…”

“Good?” Cookie smiled nervously, her hoof starting to find a rhythm. “I’ve never done it before, so —”

“It’s real good, Cookie.” Caisson breathed out, closing his eyes for a moment to just savor the feeling.

“Are you close?”

Caisson let out a breath through his nostrils. He wasn’t exactly a quickshot. From what he’d heard from other colts and sex-ed classes, stallions didn’t take much time to reach the golden plains.

Unlike them, he usually had to dedicate a good twenty minutes of ‘private-time’ in his room to climax. Time that he would usually have preferred to use sleeping. In his opinion, those other colts had it lucky.

“Just keep going,” he moaned, half-smiling to encourage his little sister.

Cookie chewed the inside of her cheek, eyebrows knitting in concentration. “Not my fault it’s taking so long.” She must also have some sense that his endurance was long — she’d taken health-ed too, of course. “It’s just so… big.”

Once again she leaned into his barrel to balance herself, allowing her to bring her second hoof back into play. Now Caisson’s head was trapped between two underhooves, each stroking with little tugs, back and forth. Cookie’s soft underhoof flesh was almost maddening against his delicate sexual tissue as she simulated the sexual grasp of a marehood.

That now-familiar ripple shuddered up from his aching testicles, as another heavy spurt of hot, clear, pre-ejaculate splattered out over his sister’s hooves and foreleg.

“D-did you… uh...” Cookie paused, pulling one hoof off of the tip and lifting it closer to her face for inspection. “Pop?”

“N-no. Sorry.”

“Stop apologizing.” Cookie giggled. Caisson watched as she brought her hoof up to her nose. “I love your smell, BC. It’s so… rich.” His heart skipped a whole beat as her lips parted and her tongue darted out to touch the slickness on her frog.

“MmmMM.” A deep hum escaped Cookie’s throat, and then rose in volume. Immediately her tentative taste became a deep lick — like a pony might do to clean a wooden spoon of thick, creamy frosting. Caisson watched his little sister’s eyes rolling up in their sockets, just before they were covered by her fluttering eyelids. All at once, she trembled, a shudder that shivered down her spine and into her rump. Her hindlegs braced, spreading wider in their stance and bending slightly, before her tail shot up straight in a fountain of flowing hair.

Splat!

There was no mistaking the source of that wet sound this time. Caisson saw the clear, steaming splash of fillycum squirt out from between his sister’s legs, splattering into a wet puddle onto the dusty floorboards of the family barn. A gossamer thread of her nectar drooled from her behind, connecting her to the spreading dampness in a long, slick, strand that belied just how lubricating his sister’s natural love-juice was.

“Ahn! B-buck!” The shudder worked its way back up his sister’s spine, making her back arch up and down, pivoting her hips up and down in an unmistakable wiggle-hump, before her left hindleg kicked out wildly at the empty air. She snorted, her head thrashing left and right.

And then it had passed.

Her eyelids re-opened lazily and uncoordinated — first one, and then the other. Cookie’s pupils were dilated and wild. Hot, heavy breaths puffed in and out of her open mouth; her tongue hungout like an exhausted husky. As those rolling, drunken eyes blinked and tried to focus on his face, her panting muzzle broke into a contended smile.

“D-did you just...?” Caisson breathed, echoing the question she had asked him only a moment before.

“Oh, BC.” Cookie purred, a tone he’d never heard from his sister before. She leaned into him, nuzzling her nose hard up his shoulder, practically grinding her snout into the muscular cord of his neck. “Yes.”

He had just made his little sister cum!

The thought made his cock jump in her hooves. She’d exploded onto the floor from tasting him! Gone were any thoughts about how wrong, how improper, how taboo this was. She was a filly. He was a stallion.

That was all that mattered.

Her neck-nuzzling face turned up toward his, as he craned his own head down to hers. Her eyes were sparkling, wild and drunk all at the same time — pupils blown wide by whatever flood of orgasmic pleasure was still boiling through her brain.

Goddesses she was so cute. So beautiful. So sexy.

So kissable.

He leaned down, his lips already starting to part as he did. He lifted a hoof to cradle the side of her face, his huge hoof wide enough to cover from her jawbone up to her ear, as he softly petted her cheek.

“BC…” Cookie breathed, close enough now that her warm breath washed over his nose. With her dreamy eyes, she took one of her still-stroking hooves off of his stallionhood, grasping his own massaging hoof, pinning it tighter against her own cheek.

“Cookie…”

They were just about to kiss, noses already touching, when physics once again reared her unforgiving head in Caisson’s love life.

Ponies were meant to have four hooves on the ground. By mathematical extension, two ponies should have eight hooves on the ground. Currently, Caisson and Cookie, in their incestuous hoofjob-kiss embrace, had managed only five hooves making contact with Mother Equus.

It started slowly, as their combined center of mass escaped their much-diminished area of equilibrium, the uneasy feeling of falling somehow mingled perfectly with the exciting feelings of forbidden love and arousal as they began to fall. Like a mighty redwood felled by a lumberpone taking a nearby sapling with it, Caisson and Cookie’s tumble accelerated faster and faster as they crashed to the ground.

A cacophony of limbs, hair, touching body parts and shared body heat arose from the rising cloud of dust that exploded up from their collapse to the barn floor.

They’d fallen on top of one another.

Author's Note

Physics is a cruel mistress.

But Cadence is a kind love-Goddess.