On the Origin of Alicorns

by MagnetBolt

Rating: mature
Tags: Romance, Porn, Princess Cadance, Fetish, Shining Armor, Sex, Twilight Sparkle, My Little Pony: Friendship is Magic
Length: 3614

Flurry Heart's birth is one of Equestria's greatest mysteries. Twilight might have finally cracked the code on what happened, but she'll need help duplicating her results...

Before Flurry Heart, there had never been an alicorn born in Equestria. It's a magical mystery that doesn't just concern Twilight Sparkle, but the ponies closest to her. She might have finally solved the puzzle, but like any good scientist, she needs to go from hypothesis to proven theory -- and the only way to do that is with help from her big brother.

Content Warning: Incest, Lewd Cadance, Breeding, A Bunch of Exposition Before They Have Sex.

An entry into the Incest is Wincest New Year's Babies Contest

Published 2020-01-29 16:20:01 UTC
Last updated 2020-01-29 16:20:01 UTC

When Stars Collide

“This reminds me of back when we were in high school,” Shining Armor said, trying to get comfortable in the somewhat undersized seat.

“Honey, if it was really like high school, you’d have Buck Withers shoving you into a locker,” Cadance teased. “But if you want to revisit the good old days, we could go find a janitor’s closet and fool around for a while while we wait for your sister.”

“We never did that back in school!” Shining Armor protested.

“If the teacher isn’t here in fifteen minutes, you’re legally allowed to start making out. It’s in the rules.”

Shining Armor gave her a look.

“It would be in the rules if I was principal,” she amended.

“I just wish I knew what this was about,” Shining Armor said. “This is the presentation you helped her with, right?”

“She had to run a few things by me,” Cadance confirmed.

“Well, you are the world’s greatest love expert, and this is going to be some kind of sex-ed thing, right?”

“Something like that.”

“I can see why she’d ask us for feedback,” Shining Armor said. “It’s got to be the most embarrassing thing to have to present in front of teenagers. You wanna know a secret?”

Cadance grinned and nodded.

“I was the one who had to give Twilight ‘the talk’ back when we were foals.”

“She told me about that,” Cadance said. “And that you had to tell her because she caught you with an issue of Playcolt and a bottle of hoof lotion.”

Shining Armor’s cheeks turned red. “She should have knocked!”

Cadance giggled. “I’m just jealous she got to see you at your best before I did.”

“Cadance, come on!”

“Isn’t that what you did?” Cadance asked, innocently. “Coming all over that magazine?”

The door slammed open. “I’m sorry I’m late!” Twilight said, hopping into the room with papers in one hoof, her wings spread for balance, and trying to scribble notes onto a scroll. “I couldn’t let Spike help me with the checklist and I didn’t realize how much he streamlines my usual process!”

“It’s okay, Twilight,” Cadance said. “Everypony gets first-time jitters.”

“First-time jitters?” Shining Armor asked. “But she’s taught tons of students in her school."

“It’s a brand-new class for a very important student,” Cadance assured him. “Do you need any help, Twily?”

“No, no, I think I’ve got this,” Twilight said. She put the papers down on the desk at the front of the room and read something off on her checklist. “Student in attendance. Check!”

“Remember to be confident!” Cadance called out.

“Hm? Oh, right!” Twilight cleared her throat. “Good morning, class. I’m glad to see you here today.” She straightened up and folded her wings, trying to look at ease even while her back hooves tapped nervously.

“Glad to be here,” Shining Armor replied.

“Now, I asked Cadance to keep the contents of the lecture a surprise,” Twilight said. “But she was very helpful in… more ways than one.”

“It’s the least I could do for my favorite filly,” Cadance said. “And the ruler of Equestria. You know, you could have just ordered us to help in any way you wanted~”

Twilight coughed and blushed, looking away. “Today’s topic is about a little-researched field of research.” She grabbed some chalk and started writing on the board. “How much do you know about alicorn reproduction, Shiny?”

Cadance giggled at Shining Armor’s face.

“I, um, I guess I’m sort of an expert?” Shining Armor guessed.

“Exactly!” Twilight said, nodding happily. “Nopony’s ever done it successfully before! Even Luna and Celestia had never seen anything like Flurry Heart’s birth. It raises a lot of very important questions.”

Cadance coughed.

“...Which we’ll cover with today’s lecture!” Twilight laughed. “Sorry. So, first, this is an advanced class, so we’ll be assuming the student is familiar with the core processes of reproduction and sexuality.”

Shining closed his eyes and nodded smugly. “You could safely assume that.”

Cadance snorted. “Shiny, I had to teach you where to find my--”

“Shh!” Shining Armor shushed Cadance.

Twilight raised an eyebrow.

“Sorry, Ma’am,” Shining Armor said, giving her a salute. “Won’t happen again.”

“I’ll allow questions from the class as long as you raise your hoof,” Twilight said. “Now, the first relevant question is, why haven’t Celestia and Luna seen foals born as alicorns? Flurry Heart proves that it is de facto possible, and any event with a non-zero chance of occurring should be replicable in the right circumstances.”

She started writing on the board, summarizing her notes. Cadance grabbed some chalk and added a picture of a smiling little filly with a horn and gigantic wings.

“While Luna has the extremely good excuse of being away for a thousand years, Celestia has a thousand years of experience,” Twilight continued. “While she decided not to give details despite my repeated appeals--”

“Twilight, you wanted her to name every pony she’d ever been intimate with,” Cadance sighed.

“It was for science!” Twilight yelled. “I would have anonymized them in the research paper!”

“A proper lady doesn’t kiss and tell,” Cadance said, primly. After a moment she felt the sheer weight of the gazes upon her and giggled. “I never said I was a proper lady. Celestia is, though.”

“Regardless,” Twilight said. “While we don’t have names we know that Celestia did get… intimate with ponies from time to time. As she never gave birth to an alicorn, it means either she was doing something wrong for a thousand years--”

Shining Armor raised his hoof.

“No, Shiny, I asked, mares and stallions.”

Shining Armor lowered his hoof.

“Or, more likely, there was some key point missing between Celestia’s experiences, which are no doubt numerous, and Cadance’s. And that missing variable is sitting here today!”

She pointed dramatically at Shining Armor.

“Uh…” Shining Armor hesitated. “I don’t think we did anything special. Cadance?”

“In our relationship, he’s the vanilla, and I’m the fudge,” Cadance said.

Twilight tilted her head. “Which means…?”

“I’m hot and get him all drippy.”

“It’s a metaphor for how Cadance spices things up at least once a week with some new idea,” Shining Armor sighed. “Most of them are a lot of fun, but sometimes I can’t sit down for a few days, or I have to wear very concealing turtlenecks.”

“This week I’ve been busy helping Twilight with her class,” Cadance said, with a wink.

“So we can safely remove technique from the equation,” Twilight said, writing it on the board and immediately crossing it out. “I eliminated it as a possibility already thanks to testimony from anonymous sources.”

“Very secret unknown sources,” Cadance agreed, nodding.

Shining Armor raised his hoof.

“Oh! A question from the class!” Twilight pointed at him. “Go ahead!”

“Isn’t it possible Cadance is the one who’s special?” Shining Armor asked. “I mean, she’s a young, recently ascended alicorn. Maybe there’s just something really different between her and Celestia. That’s way more likely than me being special, isn’t it?”

“That’s an excellent point,” Twilight agreed. “Good deductive reasoning, Shiny. It was one of the first things I wanted to eliminate as a possibility, and so I performed some medical divinations with her permission.”

She started drawing on the blackboard.

“I’m not even going to attempt to draw this anatomically, but a diagram will do. Let’s say this circle is the womb, and this little corridor is the vaginal passage. In a normal mare, the sperm travel down the passage, into the womb, hit the egg, and nature takes its normal course. Again, not going into the details there since this is the advanced class.”

Grabbing a different color of chalk, Twilight colored in the room and drew concentric circles around it.

“In an alicorn, the body contains so much magic of so many different types that instead of being wide open, the womb is a hostile magical environment. Sperm that enter simply can’t survive.”

“Unless…” Cadance smiled.

“Unless a number of conditions are met,” Twilight said. “First, the strength of the magical field needs to be at its lowest. It’s an unconscious reaction and can’t be easily controlled, so it’s necessary to put the mare at ease, in a familiar setting with a pony she trusts.”

“Should I be taking notes in case we want to give Flurry Heart a little sister?” Shining Armor whispered to his wife.

“I was thinking of something along those lines,” Cadance said.

Chalk bounced off of Shining Armor’s horn. “Hey! Pay attention in class!” Twilight huffed. “T-this is a really sensitive topic.”

“I’m sorry, Twily,” Shining Armor said.

Twilight cleared her throat. “The second condition is that the sperm have to have a high innate magic tolerance. This would require a stallion who has a large magical potential -- yes, Shiny, I can see you flexing, but muscles aren’t the same thing -- and in particular, one who has a talent with magical defenses.”

Shining Armor stopped showing off his biceps and raised his hoof. “Are you saying my special talent is why Cadance was able to get pregnant?”

“It certainly helped,” Twilight confirmed. “Or at least that’s the theory. We’re sort of working backwards from an event to find the cause. Of course, as you’ve mentioned… there are other variables. Cadance could be special in some way, it could just be a one in a million chance.”

Shining Armor sat back. “It’s not like you to have so many ‘maybe’s and ‘it could be’s in a presentation. I thought if you were getting a class ready you’d have more… I don’t know. Math? But the kind with the funny Taurish letters.”

“You’re right,” Twilight agreed with a smile. “I really need more data. That’s why I wanted you here. The truth is… I’ve been thinking about this because I got scared that I might not be able to have foals.”

Shining Armor’s expression fell. “Twily… I didn’t know…”

“It was when mom was holding Flurry Heart and talking about how great it was to have grandfoals,” Twilight sighed. “I remembered how happy you and Cadance looked, and… well, also how tired you looked, but mostly happy. Then the more I looked into it, the more I got worried I’d never have the same chance.”

“Twilight, if there’s anything I can do to help, you know I’m here for you,” Shining Armor said, standing up and walking over to hug her. “Whatever medical scans you want. You can even ask really weird questions about what Cadance and I do in bed.”

“Oh Shiny,” Twilight giggled, nuzzling him. “Cadance already gave me way more detail about that than I asked for.”

“You should have told me that this was bothering you,” he said quietly.

“I know,” Twilight sighed. “But… I wanted to make sure it wasn’t just… me being jealous. I needed a while to think about it and decide if I really wanted a foal or if I was just being silly.”

“And?”

“I decided I really, really want a foal,” she said, looking up at him. “But to do that, w-with what I learned from Cadance, I need to be somewhere I feel safe. With somepony I feel safe with.”

“Wait…” Shining Armor looked over at Cadance, who was practically vibrating in her seat with excitement. “Somewhere you feel safe. Like a classroom?”

“In a classroom with the pony who was always able to help with my panic attacks when I was a filly,” Twilight said. “A pony who is already a great father and… the pony I want most to give me a foal.”

“When you asked Cadance for help, you really wanted her permission,” Shining Armor said, with sudden insight.

“I sort of made this presentation for her,” Twilight admitted. “I was going to try and convince her to let me… you know. Be with you.”

“It was so cute, Shiny,” Cadance giggled. “She thought I was going to say no when she was practically begging me to have your foal.”

“I-it turns out Cadance is really into the idea,” Twilight said, her cheeks bright red.

“Twilight, you’ve had a crush on Shining Armor for as long as I’ve known you,” Cadance said. “It’s nothing to be ashamed of. He’s a handsome, strong stallion with a big heart and an even bigger penis.”

“C-Cadance!” Shining Armor crossed his hind legs like he could hide it.

“If there’s one thing you never have to be ashamed of it’s having a wonderful dick,” Cadance said. “And with my training, it has become the greatest cock in all of Equestria! Mares want him, stallions want to be him or at least under him!”

Twilight snorted with laughter.

Cadance got up and walked over to nuzzle her two favorite ponies.

“You two are trouble,” Shining Armor said.

“The best kind of trouble,” Cadance agreed. “What do you say, stud?”

“What would we even tell ponies?” he asked. “They’re going to want to know who the father is.”

“You tell them your wife thinks it’s hot,” Cadance whispered, leaning in to nibble on his ear.

Twilight kissed his cheek and turned away, putting her front hooves up on the desk and looking back at him, wiggling her wings and eyebrows in the way Cadance had coached her. It wasn’t perfect, but she was a quick study and Cadance had given her a cheat sheet to what turned Shining Armor on.

“I want you, Shiny,” Twilight said. “Even if I didn’t want a foal, I’d still want you.”

“Give him a show while I help him get in the mood,” Cadance said, getting down on her knees and nuzzling her way under Shining Armor’s body.

“W-Woah!” he said, surprised by her sudden intrusion on his very personal space. “Careful, honey!”

“You like it when I’m being naughty~” Cadance giggled, before running her tongue along his rapidly-hardening shaft, lapping up his salty sweat and enjoying her favorite treat.

“What does it taste like?” Twilight asked.

“If you want to find out, you’ll have to try it for yourself,” Cadance teased. “I know you’d like it~”

“Right now I only want his cock in one place,” Twilight said, raising her tail to make sure Shining Armor could get a good look at her dripping snatch, the hot scent of a mare ready to be bred filling his nostrils and bringing him the rest of the way to full arousal. Whatever reservations he might have had were swept away by seeing her like that, a mare in need of a stallion, for the first time.

Shining Armor’s hooves came down to either side of Twilight’s, his broad chest pressing against her back. His weight settled on her, warm and comforting. His cock slapped against her belly, and for the first time, Twilight understood it, the sure knowledge that she was going to be stuffed by that massive rod.

“Don’t worry,” Cadance whispered, her voice warm and reassuring instead of teasing. Twilight looked down at her. “It’ll be fine,” Cadance promised. “It is big, but your big brother is the gentlest, kindest stallion in the world. He won’t hurt you.”

Twilight nodded, offering her a smile.

“Are you ready?” Cadance asked. “If you’re having second thoughts, we can stop. It’s okay to not be ready.”

“I trust both of you,” Twilight said. “I’m nervous, but it’s nervous like waiting to open my Hearth’s Warming presents.”

“He does have a large package he wants to deliver~” Cadance giggled.

“Honey…” Shining Armor groaned.

“Here we go,” Cadance guided her love’s cock to its target, her magic tight and tingling around his shaft, keeping him hard and ready while she rubbed it against Twilight’s winking lower lips.

“Are you teasing me on purpose?” Twilight groaned.

“Half the fun is the anticipation,” Cadance said. “You don’t just want him to push you down and mount you and slam his cock into you until you’re stuffed full of his foals, do you?”

“That’s exactly what I want!” Twilight moaned.

“Come to think of it I wouldn’t mind him doing that to me once he’s finished with you,” Cadance said. “You’d better be ready for round two after this, stud~”

She adjusted his angle and slapped his flank. Shining Armor thrust forward in surprise, and the broad head of his cock popped inside his little sister for the first time, her velvety walls squeezing around him like a vice. Her wings shot out, twitching with surprise.

“Oh buck!” Shining Armor gasped.

“That’s so big…” Twilight whispered, her knees trembling. “It’s just like I always imagined!”

Shining Armor kissed her ear. “Are you okay?”

“I’m way better than okay. This feels amazing already!”

“It’ll feel even better in a minute,” Shining Armor promised. He slowly slid deeper, working his way into his sister’s depths, forcing a drop of her arousal out of the edges of their joining and trailing down Twilight’s leg.

Twilight groaned and pushed back, helping him ease his way into her tunnel until, after an eternity and a lot of hot, thick inches, his heavy balls pressed against her ass and Shining Armor’s advance came to a halt. He nuzzled her cheek, letting his weight settle a little more onto her.

“That’s so bucking hot…” Cadance whispered, raising her tail and slowly playing with her folds while she watched, letting herself edge while she watched the incestuous coupling.

“Ready?” He asked.

She nodded quickly, squeezing around him. “It feels like it was made just for me~” Twilight imagined this was how a lock must feel with its key hilted inside it, just waiting on the edge for the key to start turning and unlocking something wonderful.

Shining Armor pulled back, his broad head dragging against Twilight’s inner walls. The alicorn’s legs trembled under her, his cock stretching her so much that she almost felt like she was being turned inside-out. Before it could be painful, he reversed course, slamming it back into her.

Back where his cock belonged. Where it fit so perfectly in her aching hole. Twilight’s horn sparked, light spurting from her tip like it was being forced out of her by the stallion pistoning in and out, Shining Armor slowly picking up the pace as he grew confident he wasn’t hurting her, that she could take all of him.

Twilight pushed back against him, the heat inside her building up. Her brother’s thrusts were turning from gentle into the firm, fast, hard breeding her body was demanding. Shining Armor’s breath was hot against her ear, his weight pinning her to the desk while he made Twilight his mare.

“Give me your foals!” Twilight begged. She’d never felt so receptive, so needy. Just the idea of being swollen with his foals was pushing her to the edge.

“As you wish,” he panted, and his stance changed, just a little. His thrusts came faster, shorter, slamming the tip into her depths.

And that tip flared, spreading her innermost depths even wider, the broad tip pressed up against the entrance to Twilight’s womb. Shiny’s teeth found her shoulder, biting her, not hard but firm, holding her in place.

She cried out wordlessly as his virile, powerful seed filled her, his flared tip keeping it from escaping. His heavy balls drained into Twilight’s foal forge, and the sensation sent her over the edge in the strongest orgasm she’d ever had.

A massive bolt of magic erupted from her horn, inches from Shining Armor’s face. He saw his life flash before his eyes. He’d spent a lot of time masturbating, and he was starting to notice how often Twilight had caught him.

“Oh-- oh stars, are you okay?” Twilight asked, starting to panic. “I swear, that hasn’t happened in years!”

“I’m fine,” Shiny said, letting go of her ear and looking up at his bangs. They were a little crispy, but he was otherwise unharmed.

“Well, um, that was a little unexpected but I think otherwise, that went… perfectly,” she sighed, smiling and squeezing around his slowly-softening shaft.

“I’ll say!” Cadance agreed, from where she was perched, watching their joining from a very intimate angle, her tail twitching with excitement. There was a puddle between her legs from her own arousal, and she turned onto her side to let them see her needy, swollen slit. “Once he’s done with you, I think I’m going to need him to give Flurry a little sister~”

“Two data points would be excellent,” Twilight agreed. “A-as long as you don’t mind me watching. For purely scientific purposes! I have to be able to take notes or it isn’t science.”

“So, um, when will we know if it worked?” Shining Armor asked. He adjusted his weight, not pulling out but getting his weight off her.

“It can take days before a spell will be able to tell,” Twilight said. “Maybe a week?”

“Do you think it would muddle your results if we ran the experiment a few more times?” Shining Armor asked. “I was thinking… if it works best where you’re relaxed, the Canterlot Archives have a lot of dark corners and private rooms…”

“Oh my gosh, the Archives?!” Twilight gasped. “But I could never…” she bit her lip.

“You’re a Princess, Twilight,” Cadance giggled. “You could even build a book fort! Or a book harem! That’s even better. You could make it out of copies of the Pony Sutra and the best selections from the Romance section!”

Twilight shivered with forbidden desire. Even more taboo than being mounted by her brother.

“From what I can feel down below I think she likes that idea,” Shiny said. He leaned down to kiss Twilight. “I love you, sis.”

“And I’ve got the best big brother in the world.”