Big Brother Best Lover Forever

by thathornypony

Rating: mature
Tags: Twilight Sparkle, My Little Pony: Friendship is Magic, Princess Cadance, Porn, Fetish, Random, Shining Armor, Sex
Length: 3036

Cadence catches Twilight and Shining Armor doing it. As punishment, she fucks them both with her big futa cock.

Twilight Sparkle and Shining Armor have a very close relationship. They are brother and sister, and best friends forever. But there is another aspect of their relationship that they don't tell other ponies about. They like to fuck. A lot. But that's okay, they're best friends, remember. What's a little incest between friends? Oh, just be especially sure not to tell Cadence. Who knows how that would turn out.

Contains: brother/sister incest, futa, gender swapping, cum inflation, excessive cum, bukkake

Published 2018-07-08 08:00:07 UTC
Last updated 2018-07-08 08:00:07 UTC

Chapter 1

Twilight strode into her room perfectly drunk. She wasn't staggering or stumbling around, but the world had a delightful fuzz hanging of it. It helped that her brother was there to show her where her room was. Even sober she was not an expert at navigating the palace of the Crystal Empire. "Thanksh, Shiney," she said.

"No problem," he said, watching as she bee-lined for the bed. He couldn't help but notice that his inebriated little sister wasn't that little anymore. She hadn't been for a long time, but between how rarely he saw her and what becoming an alicorn had done to her, well, she was quite the mare.

"Enjoying the view?" she asked suddenly.

He realized that she had taken a seductive pose without him noticing. "I—yes," he had to admit. "Look, Twiley, you're drunk, are you sure you know what you're doing?"

Twilight cooed at him. "It will take a lot more than a few drinks to disorient me. Come on, " She patted the bed next to her, "Just like old times?"

"I'm married now! We can't do that anymore!" He tried not to remember the long summer nights they had spent together as foals, the camping trips... But his dick remembered, poking out of his sheathe.

Twilight pouted, "Just one more time then? Just once, it won't hurt. Besides, Cadence knows our family. She'll understand."

Shining Armor looked at her. He did not say anything—even when her magic shut the door behind him and she started slinking over to him. His eyes followed her full flanks. There was a good bit more Twilight Sparkle here than he was used to; the look suited her, he thought.

His refusal to react lost all credibility as declining her when he remained still even as she crawled under him and wrapped her lips around the head of his dick. It was still soft, but in the socially unacceptably familiar warmth of her mouth, it quickly began to grow.

He stood stoically, eyes closed. He didn't dare watch as she sucked him. She kept her lips planted right at his base, so that as the blood rushed in, his cock expanded directly into her throat. Celestia damn her, he thought. She had tried this trick many times before, never successfully. But now with her newfound height, it looked like she was going to pull it off. He groaned it felt so good.

He opened his eyes and looked down. She was mostly underneath him, the only part of her visible was her rump. He sighed, there wasn't really any point in holding back now. He grabbed her flanks with his magic and pulled, spreading her pussy wide. An ethereal dildo appeared behind her, shimmering violet. He glanced straight down. His sister was so engrossed in his cock that she'd never see it coming.

It plunged into her; the reaction was immediate. She gagged loudly on his cock, where previously she had only been slurping. She was a skilled cocksucker—he was proud to have trained her—but she was not a quiet one.

He fucked her with his magic. If not for their past experiences, Shining wouldn't have believed she could get as much more enthusiastic in her oral ministrations as she did.

Shining Armor loved his little sister.

He was rock hard. It had been a long day and he needed this. Even if it hadn't been, Twilight's throat felt so amazing that he would have gotten as desperate to cum as he was even coming straight from an orgy. He didn't tell her it was coming; he never had before and he wasn't about to start now.

He didn't notice how long she had been down there. He was so used to alicorn blowjobs at this point that it no longer even occurred to him that most mares would have come gasping for breath two or three times in the time Twilight had had him hilted in her mouth. Every inch of his stallionhood was covered in soft, twitching, wet, warmth.

It was one of those times where you know you've passed the point of no return a good couple of seconds before the orgasm actually hits. He felt like he was floating as his muscles started tensing to shoot out his load as Cadence opened the door.

She walked in and locked eyes with him, watching calmly as he came down his sister-who-was-not-his-wife's throat. He didn't say anything. What could he say? He just tapped Twilight's shoulder urgently.

She disgorged his cock; slime dripped from her mouth and jaw. "What is it. bro..." She trailed off as she saw Cadence. She turned pale. "Okay, this isn't what it looks like. I was just—"

"'Not what it looks like,' huh?" Cadence said, taking a step forward. Her voice was perfectly level.

"Twilight, don't, just let me handle this," Shining whispered out the corner of his mouth.

Cadence continued. "Because from where I'm standing, this looks like at least a seven."

"A seven!?" Shining and Twilight said at the same time. He shushed her, then, "You have to be kidding. It's definitely a five. Six at most. She is my sister, after all."

Cadence stared at the two of them. Finally, "Six—and a half."

Shining raised his hoof to say something, thought about it for a second, and put it back down. "Okay. Six and a half."

Twilight was very confused. "I don't understand. What do all the numbers mean?"

"Its complicated," Shining said, "I'll explain later. But for now, do you have your sex spells ready?"

"Lubrication and Birth Control? Yeah, I could cast them in my sleep." Twilight said, mystified.

"Good." Shining nodded, looking at his wife. "You're going to need them."

Cadence smiled. It was not a friendly smile. "It's good to see you remember some of your manners." She closed the door behind her. And locked it. And cast a soundproofing spell on the room. "Let's get started, then."

Her horn glowed cyan. The light grew brighter and brighter, and it spread until it had enveloped her whole body. The two siblings had to shield their eyes. When the light faded, Cadence was different, she was bigger, taller. There was a giant crystal cock between her legs.

Shining stepped in front of Twilight. "The important thing you need to know is that Cadence and I have a deal. Everything is going to be fine, just go along with all this," he said to her. Then to Cadence: "Let's do this."

Cadence smiled, more genuinely. A beam of light shot out of her horn and hit Shining; he crumpled to the floor.

"Shiney!" Twilight yelled and rushed to her brother. She put her hooves on him and shook the...mare in front of her.

Her jaw dropped as Shining got up. She was a lithe mare, sleek where she had been muscular just a few moments ago. Something somewhere in Twilight grumbled. Her brother was even hotter as a mare than as a stallion.

She didn't get much of a chance to look at her sister, though. Cadence grabbed Shining's head with her magic, and, without ceremony, yanked it forward and started to facefuck her.

Twilight could only watch as Cadence's cock plunged down her sister's throat. Her loud gagging noises a testament to in inexperience in giving blowjobs.

Shining Armor knew there was nothing to do but let it happen. A deal was a deal, and she was more than willing to go through this to maintain his relationship; she was more worried for Twilight's sake. Besides, although she would never admit it, she enjoyed this a little. Even if she would have preferred it if Cadence had been a little bit less rough as her literally rock hard boner forced her jaws open.

Meanwhile Cadence was still annoyed. She had known about the Sparkle family traditions for a long time, but would have been the least Shining could do to tell her what he was going to get up to when Twilight came to visit. Fortunately, nothing burned off stress like a good round of fucking. And even more fortunately for Shining's magically feminized holes, Twilight was here to assist her in blowing off steam.

Mmmmm, she thought. Shining had a nice mouth when he was a mare. He had a nice mouth when he was a stallion too, but they both preferred the mare route. In any case, she felt it was about time to start enjoying the advantages of magical crystal marecocks over regular cocks. She pushed down into Shining's throat. She concentrated and willed herself to cum. Her penis flashed as it started to pump rope after huge rope of cum into her husband's stomach. She pumped and pumped, and when she felt she had had enough, she pulled out a little to fill her pretty little mouth.

Shining swallowed the first few surges. But even if her stomach hadn't already been full, there was just too much. Hot sperm spilled out of her mouth, and she reared away from Cadence.

Cadence caught her hooves with magic, and forced to spin around and bend over, presenting her rump.

Cadence decided to go for the ass first. Shining didn't really enjoy having things up his butt in any form, so she thought she'd get it over with for her. She pressed the glass smooth head of her cock against Shining's ponut, and leaned into it, feeling it stretch around her. She stopped as soon as the tip was completely inside, and made willed another cumshot.

Shining squirmed as the crystal pulsed inside her. Each pulse bringing with it a warm wave. She felt the cum dripping, flowing, flooding deeper and deeper in her. She grit her teeth as she suddenly started to cramp up.

Cadence felt it too. Satisfied that she had completely filled her husband's colon, she pulled out, and a nice little wave of cum glopped out with her. Now it was time for the prize: Shining Armor's vagina.

She plunged mercilessly into the former stallion's cunt. And she fucked her like the nag she was. Hard.

Part of Shining was embarrassed that Twilight was seeing her brother get fucked like a mare, but that was a small part. Most of her only knew that getting fucked felt damn good and wanted to enjoy it. She only ever said it to Cadence, but using a pussy felt a lot better than using a dick. There was so much more area inside to touch and to thrill. The urge to stick one's dick in things, and the satisfaction from actually doing it, paled in comparison to the sheer need that having an empty hole, a gap produced, and the sublimity of having it filled. Cadence was always quick to remind him that he only ever had a pussy for a few hours during sex and she had to live with one, and if he wanted to try it out full time she would gladly switch, but he was never really in the mood to do that.

Point was, even for a stallion getting railed hard is pretty enjoyable if you don't think about too much.

Cadence thought that her husband had been so cooperative, that she deserved a reward. She let her magic tickle Shining's clit. At once the mare underneath her who had been only grunting slightly with each stroke began panting and squeaking—it was adorable. She intensified the magic and let Shining cum.

And this was the part where Shining had no problem admitting he was jealous of mares. "Fuck!" her screamed as he convulsed on Cadence's cock. "Fuck fuck fuck fu-fu-fuuu." She could feel every inch of Cadence's dick as the walls of her pussy contracted tightly around it.

Then Cadence decided it was time to treat herself again. She came as hard as she could, splattering the insides of Shining Armor's pussy with her seed. Then filling its depths. She continued. Semen squirted out around the edges of her dick and got all over her belly. At last she pulled out, letting her husband collapse on the floor, thoroughly filled, bloated, with pints of cum.

Then it was time for the real show. She stepped towards Twilight. "Your turn now. I'm feeling a lot nicer, so I'll let you decide which of your holes I ruin first."

Twilight was still staring in awe at the fucking her sister had just gotten. She barely registered Cadences words. When they did come home, she said, "I, uh, wow, I guess I started all this by blowing him, so, my mouth?"

"An excellent choice," Cadence said.

Twilight's world blurred. She didn't know if she had moved, or if Cadence had moved, she just knew that Cadence's cock was balls deep in her throat before she so much as blink.

She choked. Hard. She had sucked dick before, but usually she was the one in control of the situation. Not here. Cadence's assault on her face was relentless. She felt Cadence's balls hanging over her chin. She couldn't get the slightest gasp of air past the massive rod in her mouth, throat, and even stomach from what it felt like. Until Cadence pulled out, but that was only for a moment to slam it back in. Twilight couldn't react; there was nothing she could do but let Cadence use her. There were worse things.

Soon Cadence got bored of widening Twilight's throat. There were more interesting places around back. But she couldn't just let Twilight go on an empty stomach. She unleashed a another torrent of cum. This time she let her injection continue just a little too long, so that when she pulled out, Twilight yakked out a bunch of the salty slime in addition to what Cadence had filled her mouth with.

She decided to go with the same order for the back holes that she had used with Shining, though she had no intention of being as gentle with Twilight's asshole. She lifted her sister-in-law into the air. Then she climbed onto the bed and sat. Her cock pointed straight up in the air. She lowered Twilight onto it, delving deep into her ass. And deeper. And deeper. Twilight had started this, so she got the full package—all the way to the balls. Ooh and Twilight's colon felt gooood.

Twilight was fine until she felt Cadence's medial ring pressing on her hole. When the pressure didn't let up, she said, "Uh Cadence? Don;t you think that's far enough?"

"No," Cadence said. "You realize this is me getting back at you for blowing my husband behind my back. This is for my enjoyment, not yours. Don't worry, though. You're a princess now. You're immortal alicorn body can take a lot more than a normal pony. I intend to take full advantage of that."

Twilight's eyes went wide as she suddenly sank the rest of the way down Cadence's dick. Oh Celestia, she could feel it moving around inside her, and moving things around that weren't supposed to move. It didn't hurt, but it felt like it should have. Then the fucking started again.

Cadence shook Twilight in her magic like a living fleshlight. In truth, Cadence didn't like fucking like this all that much. The hard crystal of her marecock was good for intimidation, not so much for sensation. Still, what she was doing was pretty hot, and she could appreciate that. She appreciated it enough to fill Twilight's ass with cum. She was impatient. She wanted to get to the main course.

She lifted Twilight off her, holding her in her magic like a used condom; she was sure dripping cum like one. She set her down in the position. She took a moment to relax and enjoy the sight of Twilight's pussy. It was a nice pussy, she could see why Shining liked it. Too bad for him she was about to claim it.

For a third time Cadence rammed her dick into Twilight Sparkle. Deep into her cunt. Twilight was still disoriented from the ass reaming she had just gotten, but she definitely noticed when Cadence shoved her cock through her cervix and into her womb. She screamed.

"Oh hush," Cadence said, hilting herself in Twilight's pussy, "It doesn't hurt that bad."

Twilight was about to yell at her about that, but she noticed she was right. The initial pain, while sharp, was fading fast, leaving a strange sensation. Parts of her were being stretched and filled that had never been stretched before. As she sat on Cadences dick it actually started to feel pretty good.

Cadence didn't wait for Twilight to ponder these new feelings. She had a mare to fill. She focused her magic in her cock to produce an extra large load.

Twilight gasped as she started to deliver it. Cadence flooded her womb with hot, virile seed. The flood continued and Twilight felt the chamber expanding as the pressure grew, and grew. She watched as her belly swelled up. Oh Celestia, it felt like she was going to pop. And yet every second she was surprised by how much she could take. She might have been cumming—something felt good—but she wasn't sure. She wasn't sure of anything that was going on.

Cadence stopped. Twilight was starting to get delirious. She pulled out and let the mare collapse next to her sister. Cadence was impressed. Twilight had taken everything like a champ. She was so bloated with cum she looked bigger than Cadence herself had at her most pregnant.

Okay, Cadence couldn't be mad anymore. Those two did look pretty cute together. She saw no reason not to let them continue their games, as long as Shining remembered who was boss of his dick. On that note, she thought of a final present to give them, though it wasn't much after everything else she had given them. She stood above them and came one last time. Stripe after stripe painted their sleeping bodies. Soon they were covered horn to tail. There, that was better. Cadence banished her dick, and turned Shining back into a stallion. Then she lay down with them—she was tired too—one big happy, sticky family.