"Wow... That escalated quickly," Night said, sitting on the edge of the bathtub across from his wife, still sitting on the toilet as her son's copious seed continued to drip from her marehood.

"You're telling me," Velvet groaned. Shining and Twilight were both still passed out on their parents' bed. "There is a point where we needed to stop and we have clearly passed it," Velvet said.

"Which point was that?" Night asked. "When you decided to let your own son fuck you?" Velvet wiped the last of Shining's cum from herself and flushed. "Or when you said I should do the same with Cadance? Or maybe it was when we decided to give up Cadance in the first place and go along with this whole crazy plan of Celestia's?"

"Can I have some water please?" Velvet asked. Night Light grabbed a couple cups and filled them with water from the sink, giving her one of them. She held her cup and looked at it. "Maybe it was when I decided to go home with my brother from the Gala," she said, giving him a smirk. He just sighed and smiled back.

"To the first of many bad decisions," he agreed, tapping his cup against hers in a toast. "So what do we do now? I mean, we have to tell them that what we all did was wrong."

"It wasn't!"

"You know what I mean! Yes, I get that our family is unusual, to make the understatement of the century, but we need to explain to them that the rest of society will think that what we did was wrong. At the very least, we can't have them telling anypony else about it," he said.

"Yeah, you're right," Velvet agreed. They walked back to the bedroom and sat on the bed, rousing their children.

"Shining, Twilight?" Night said, nudging them awake. "We need to talk to you about what you just learned." Shining and Twilight woke up and sat up as they rubbed their eyes.

"Are we taking a quiz?" Twilight asked, excitedly. Even Shining looked eager to 'learn more'.

"No, it's nothing like that," Night said.

"There are a few more things that we need to tell you about sex," Velvet said. "It's more important than the types of sex, or techniques."

"Always practice safe sex," Shining said.

"That is an important point to remember too," Velvet agreed. "But there's more. Specifically about this lesson today. Because most ponies aren't home-schooled like this. They learn about sex in a classroom. And it's just a boring lecture without any of the... interactive learning we did. They just talk about it."

"And even other ponies that are home-schooled just talk about it," Night Light said. "They don't actually do it."

"Why?" Shining asked.

"Well... sex is just supposed to happen between ponies that love each other," Velvet said.

"But I love you, Mom. Don't you love me?" he asked.

"Of course I do, Dear. But it's different," Velvet said. "Sex is supposed to be between ponies that are in love, like your father and I. Ponies that get married. The love between family members is different," she said, practically tasting the hypocrisy on her tongue. "Family members shouldn't have sex."

"Why?" Twilight asked.

"Well, if family members have a baby together, the foal could be very sick because of how close their genetics are," Velvet explained.

"So as long as you use a contraceptive, and you don't have a foal, it's okay?" Shining asked. Velvet grit her teeth.

"No," Velvet lied. "It's wrong to do it. Which is why what we did today must remain a secret."

"Why?" Twilight asked.

"Because ponies will think that it's wrong for family members to do that. Society will think that it's wrong. That's just the rule."

"But why?" Twilight asked again. "If they're not having a sick foal and nopony is getting hurt, then what does it matter? It seems like a silly rule." Velvet felt very proud of her daughter in that moment.

"You know what, Twilight? You're right. It is a silly rule. But it's sort of like picking your nose. There's nothing really wrong with it, but you still don't want to get caught doing it."

"So as long as we don't tell anypony, we can keep doing it?" Shining asked excitedly as he moved closer to his mom. Night Light cleared his throat loudly and wrapped his hoof around Velvet.

"Shining. I'm your father's mare. And he's my stallion. So that is just something that he and I do together as a married couple. We made a special exception today to teach you both about sex. But that's it."

"Oh." Shining was visibly disappointed.

"Besides, you should be more interested in fillies your own age," Night said. "Somepony like Cadance."

"I guess," Shining said.

"Speaking of," Night Light continued, "Cadance will be here for next weekend to watch after you while your mother and I go on a little trip. Twilight, I know how much you wanted to see her again."

"Yeah!" Twilight said excitedly. "But we really don't need a foalsitter to watch over us anymore."

"We know," Velvet said. "But your father worked very hard to... persuade her to come back for a weekend while we go on vacation."

"It will just help to make your mother feel better while we're gone," Night said.

Friday evening, a knock came at the front door. Velvet turned the knob and opened it.

"Cadance!" she greeted the pink alicorn. They shared a hug and Cadance presented her with a platter. "What's this?" she asked.

"Just a little something I baked. I know how much Mister Light likes brownies," Cadance said.

"Oh, he is going to be disappointed," Velvet said. "We're actually on our way out, now. Sorry to drop it on you last-minute. But yeah, we're going out for the weekend. But you've got this, right?" They both turned to look at the carriage pulling up to the curb. "Night!" Velvet called into the house. "The cab is here!" Velvet quickly put the plate of brownies on the kitchen counter and walked back to Cadance at the door.

"Sure. What are foal-sitters for?" Cadance said with a saccharine smile. Velvet smiled back and walked past Cadance outside to the cab. Night Light hustled down the stairs with his bag.

"Hi Cadance," he said as he neared her. "Sorry about the short notice on our trip. We should be back Sunday night. If you need anything... well, I'm sure you'll have everything under control."

"You're not going to be here... with me?" Cadance asked with sad, doe eyes.

"Sorry, no." He moved to walk past her. She put a hoof up to stop him.

"Am I going to have to get this meal... to go?" She grinned at him as her horn glowed. He felt her magic on his crotch, teasing his sheath. She could tell he was starting to get hard.

"Night?" Velvet called from the curb.

"I'm coming!" Night shouted.

"Not yet..." Cadance whispered.

"Enough!" he growled, countering her magic. "I am still a married stallion."

"I'll stop doing it when you stop enjoying it," she said. "Just tell me that you honestly don't like it. But don't lie to me." Night Light just stared at his daughter for a moment.

"I have to go," he said. It wasn't a yes.

"Mhmm. That's what I thought. See you soon, Stud," she purred. He huffed and trotted past her. She watched his toned flanks as he stepped up into the carriage with Velvet. The cab began to roll away and was out of sight within moments. Cadance turned and walked back inside the house and closed the door.

"Cadie!" Twilight squealed from the top of the stairs as she bounded down and ran over to hug her. "I missed you!"

"I missed you too, Twi," Cadance said, feeling her frustration with Night fading away. Her desire aside, she really did value her time with the filly. Or rather, the mare now. "Wow, you've certainly grown since I last saw you. Where's Shining?"

"He's in the bathroom."

Meanwhile, Shining Armor was busy exploring his new discovery: Himself. His hoof was a blur on his shaft as he felt his climax approaching. In moments, he turned the toilet bowl into a Jackson Pollock masterpiece. Once he was finished he flushed and washed his hooves. 'It still wasn't as good as the real thing,' he thought to himself as he scrubbed that last of it from his hooves' fur while his penis retreated back into its sheath. The feeling of being inside a mare was still fresh in his memory. And as arousing as the thought was, his fresh release gave him some respite from his physical reaction.

He walked out of the bathroom and headed into the living room to greet Cadance. Twilight was already regaling her with tales from her first year at Celestia's School for Gifted Unicorns. Shining had already heard the bulk of the stories over the preceding days. Cadance caught his eyes and gave him an exasperated look. He knew how she felt. Once Twilight got to talking about something, she could have a real motor-mouth. Shining just settled into the living room chair and zoned out, listening to the mares on the couch.

"Well, it's getting late," Cadance said some time later as she stretched her legs. "And it was a long flight in, so I'm going to turn in for the night. Your folks aren't home, so feel free to stay up as late as you like." Cadance got up and walked upstairs. Twilight and Shining watched her walk to their parents' bedroom.

"That's Mom and Dad's room," Twilight said.

"Yeah, your dad said I could sleep in their bed for the weekend," she lied.

She stepped inside and closed the door. She walked around to the far side of the bed and leaned over Night's pillow, smelling it. She could tell right away that it was his. She climbed into the bed and pressed her face into it, relishing his scent as she put her hoof between her thighs.

"So what do you want to do now?" Twilight asked Shining. He shrugged.

"I don't know. I'm not tired at all. I'm actually a little hungry," he said.

"I saw that Cadie brought over some brownies. They're in the kitchen," she said. They walked into the kitchen and unwrapped the dessert platter. Sure enough, there were a dozen brownies that Cadance had made, meant for Night Light.

"Dinner is served," he said, taking several. Twilight followed suit.

"Should we leave some for her?" Twilight asked. Shining shook his head while he finished chewing. He pointed at the pantry.

"She can always make more. We have all the ingredients. You love baking with her, don't you?" Twilight nodded as she ate a couple herself.

"That's true," she agreed. "Hey, do you want to play Scrabble?"

"No. You always kick my ass at it," he said between bites.

"Please? We can do what you want after," she said. He rolled his eyes.

"Ugh, fine," he resigned. Twilight ran into the living room to fetch the game while Shining grabbed the rest of the platter and put it on the table. They set up the board, the rack, and their tiles.

"Do you want to go first?" Twilight asked, offering the double word bonus of the first word played.

"Gladly. Light. With the double word bonus, that makes it 22 points!" he said, writing down the score. He drew some more tiles while Twilight added three letters to the beginning of it, reaching the Triple Word bonus.

"Twilight. Triple Word is 45 points," she said.

"You can't use proper nouns, like names, Twilight," he said.

"It's also the time just after sunset, you doofus!" she teased, writing down her score.

"Okay fine. Shin," he said. "A part of the leg."

"I know what a shin is," she said, adding to it. "Shining."

"No names!" he said.

"It's what the moon is doing right now," she said, pointing out the window.

"Oh yeah. Hey are all names like that?" he asked.

"No. What about Cadance?" she asked.

"It's a thing that we do in the guard, sort of like singing when we march," he said. They both scratched their heads thinking of all the ponies they knew.

"Celestia!" Twilight said.

"Doesn't it mean 'the sky'?" he asked.

"No, that's celestial," she said.

"Okay. I guess that's one. It's my turn, right?" he asked. She nodded and they continued playing. The board slowly filled up.

"Quixotic," Twilight said, laying the tiles across the last Triple Word bonus.

"That's not a word! You made it up," he accused.

"All words are made up!" Twilight retorted. She pushed the dictionary across the table. He angrily opened the book and looked up the word.

"Quixotic: Exceedingly idealistic; unrealistic and impractical," he read aloud.

"128 points!" Twilight declared, utterly trouncing his score.

"Dammit!" Shining cursed and slammed the table with his hoof, scattering the tiles onto the floor.

"Hey!" Twilight yelled, getting out of her chair to pick up the tiles. She ducked under the table to gather them up. That was when she saw it. Shining's huge erection. It wasn't a very large table. Just by being under it she was practically face to shaft with him. She felt her nethers itch as her tail reflexively lifted. She was certain that she had taken her Beat the Heat potion that morning. But that evening she had the itches worse than she'd ever had before. She shifted her hind legs and unconsciously leaned closer to it. Shining leaned over and looked under the table, seeing his sister staring at his crotch.

"What are you doing?" he asked. She snapped out of her trance and looked at him, getting angry again.

"Cleaning up your mess!" she said as she started to gather up the tiles. "Why don't you get down here and help?"

"Fine," he huffed, kneeling on the floor beside her. The started scooping up the tiles. She occasionally stole glances at his shaft bobbing under him.

"So why is it like that?" she asked.

"What?"

"Your... penis. Why is it like that right now? I though it only did that when you first woke up in the morning or when you took a bath," she said.

"Yeah. But sometimes it just happens. Like if I think about... sex stuff," he said.

"You were thinking about sex stuff while we were playing Scrabble?" she asked.

"No. It just sort of happened. I don't know why. But, yeah, now I am," he said. Twilight waited for a few moments.

"Like what?" she asked.

"What?"

"Like, what sex stuff are you thinking about?" she asked. His cheeks turned pink.

"Mom. I was thinking about when I... when we did it," he said. "It felt really good. Like... the best thing. I wish we could do it again."

"Yeah," Twilight agreed. "When Daddy gave me an orgasm, it was the best! I tried to do it with my hoof and my magic, but it just isn't the same."

"Yeah, I know what you mean," he said. She turned to get the last few tiles under her chair. Her tail brushed across his face, soaked in her musk. He hadn't noticed it consciously before. But now he was aware of it. It was that good smell that was unlike anything else. Pheromones, he remembered. He could see Twilight's clitoris winking out of her marehood at him under her flagged tail. He leaned closer to smell her better. She backed up into him, mashing his nose into her pussy. She yelped and moved away from him as he reflexively licked his nose. His erection was so hard now that it almost hurt.

Twilight turned back to face him as she forced her tail down to cover herself. She felt like her loins were on fire. Her hooves pawed at the floor in desperate frustration. She could see that Shining likewise had a pained expression on his face.

"I- I think I need something to drink," Twilight said. She crawled out from under the table and put the tiles bag in the game box before heading over to the fridge. Shining followed closely after her. He practically had his face in her tail as she leaned down to get the pitcher of apple juice from the bottom shelf. She turned around and collided with him, getting juice splashed on both of them. "Gah! What the heck!" Twilight snapped at him being so close behind her.

"Oh, uh, sorry!" he apologized, backing away in shame. But the damage was done. The sugary juice was already seeping into their fur and manes, making them sticky. Twilight set the pitcher on the table and then stood aside while Shining quickly wiped up the mess on the floor. She chewed her lip and shifted uncomfortably in place as she watched his erection bobbing beneath him as he worked. "I need to go get cleaned up," he said, scurrying to the bathroom as soon as he was done.

Shining turned on the water for the shower and stepped inside. As much as he usually enjoyed soaking in a bath tub, his time in the Guard Academy had taught him the efficiency of taking a shower. He rinsed off and reached for the shampoo, but felt another, more pressing matter that needed to be dealt with. But his hoof just braced against the shower wall while the other reached under him. He had gotten good at using his magic on himself. But the running water made it difficult for him to use magic. Even so, he couldn't very well go back out there in such a state around Twilight.

He started to stoke himself under the warm water's spray. It was as much the reason for the shower as the apple juice. His mind wandered to the usual fodder while he masturbated. He thought about the other week when he had first discovered masturbation and sex. He especially thought about his mother, and how it felt when she let him-

He heard the bathroom door open and the the shower curtain was pulled aside. Twilight stepped into the shower behind him.

"H-hey! What are you doing?" he yelped at the intrusion, quickly trying to make it look like he wasn't just beating off.

"What? It's not like we've never bathed together," she said. "Besides, I need this more than you do." It was true. Being shorter than him, she'd taken the brunt of the splashed juice. It had gotten into her mane, and much of the fur on her back. "Now move over before you use all the hot water." She shimmied past him while he tried to cover himself with his hoof. Twilight rolled her eyes. "Please. It's not like I've never seen it before."

She was right, he realized. She had seen it before plenty of times. Why did he suddenly care if she saw it now? Why did he suddenly feel ashamed of her seeing him like this? Was it because of what he was just doing? Shining stood and wondered in the far end of the shower while Twilight stood under the warm water. He watched her bathe while he was still unbearably horny. He felt a twisting feeling in his gut as his thoughts of sexual fantasy shifted from one mare... to another.

"Do me?" Twilight asked.

"W-what!?" Shining balked. She passed him the soap.

"My back?" she asked. He looked at the soap in her hoof.

Do her? Oh, wash her! he realized. He took the soap and began to rub her back with it, creating a nice lather.

"Mmm, that feels nice. Get my shoulders?" she asked. In the confined space of the shower tub, he didn't have much room to maneuver. He did his best to lean over her while keeping his lower half a safe distance from touching her. She backed up a little closer to him as he worked, causing her tail to drape over his erection. He looked down and realized that despite the weight of the wet hair, her tail was still flagging high, exposing herself to him.

Her tail teased his penis and his shaky leg stepped forward to catch his balance, sending his penis under her, between her legs. It grazed her inner thigh. Her legs reflexively snapped shut, but it only served to trap him between her warm, wet thighs. His hooves grabbed her waist on instinct, pulling her back to him as he pushed forward. The texture of his shaft rubbed against her marehood.

"What are you doing!?" Twilight asked.

"I don't know!" Shining said. In truth, he understood perfectly well what he was doing. But he didn't understand why he felt compelled to do it. Not that he had anywhere near the capacity for abstract reasoning at the moment. All he felt was the need. He thrusted again, sliding it between her soapy thighs.

Twilight felt his medial ring graze against her clitoris as he did, making her shudder with the pleasure she'd been unknowingly craving. It served to both ease her ache, and yet intensify it further. She, too, though of their mother. She remembered how worked-up she felt when she watched her taking a stallion into her. She remembered the moans of pleasure her mother made when she was brought to orgasm by both of the stallions that day. She remembered how badly she wanted to be her in that moment. She wanted to feel it. No, she needed it. And she needed it now.

Sliding it in and out between her legs felt better than using his hoof, Shining decided. But it was a far cry from the memory he had with his mom, of the time it was actually inside a mare's vagina. He started to lose focus as he lost himself in the fantasy. He pulled back a little to far and pulled it out from between her legs. It sprang upwards a little and when he went to push forward again, it pressed against her hot marehood. It parted her lips, his tip poised at her entrance.

They both very-well understood what sex was, and the significance of virginity, at least for a mare. Even in the haze of their lust, it gave them a fleeting moment of sober clarity. Shining froze his movement, realizing that they were on the threshold of a very important line they weren't meant to cross with each other.

"We really should stop," he mumbled, summoning his last shred of willpower to pull away.

"No," Twilight stopped him, reaching back and holding him in place with her free hoof. "I want this too!" She pushed herself back against him.

And just like that, he was inside her.

With her ache finally being seen to, she was too overcome with with her need and pleasure to even notice the brief twinge of pain inside her vagina. The pain passed without fanfare, as did the unnoticed, crimson droplets, heralding the significance of the event, being washed down the shower drain.

"F-ff-fuuh!" Shining couldn't even find the words. It was just like he remembered with his mom. Better even. She pushed herself back further, urging him to continue. Shining needed no more encouragement. He wrapped his hooves around her and pushed himself forward into her. As eager as he was, she was still his little sister and he wanted to try to be gentle with her. Shining understood the mechanics of the motion well enough. Twilight braced her hooves against the far wall and moaned. Shining Armor and Twilight Sparkle began to have sex.

With each of his first few thrusts, he pushed a little deeper. Though she was an adult, she was still not yet fully grown. As a result, he was nearly all the way inside when-

"Ow!" Twilight yelped as she felt him bump into her innermost barrier. She had never felt so full in her life. He felt himself reaching a dead end with barely an inch of his length left.

"So close!" he whined. Twilight lowered her hooves from the wall and bent over, leaning down towards the tub floor. The new position angled her pussy so that her clitoris was closer to him, and it served to cause her insides to shift a bit upwards, yielding just a little bit more space for her big brother. He pushed in just a little more, resting his balls against her winking clit. It had taken some doing, but at last they were "A perfect fit!" he said. She couldn't agree more. He was content to just keep himself there, buried deep inside the wonderful embrace of a mare.

"Okay," she breathed. He understood and began moving his hips again. He made long, slow strokes. He understood that once he came, that would be the end. He wanted this to last as long as he could. A tough task, as she was much tighter than their mother. But having two (or three) foals could do that, he reasoned. Each time he sank into her, his balls would press against her clit, making her shudder. Feeling her pussy quiver around him was not making his mission for longevity any easier.

"Faster," Twilight begged.

"Twi, I-"

"Faster!" she demanded. Twilight struggled to cast the contraception spell under the running water. Shining would not deny himself a good time any longer. He complied with her wish and thrusted faster. His balls smacked against her pussy with wet slaps. "Oh. My. Gosh!" Twilight's knees trembled as she felt herself cumming. Her pussy squirted out from around his penis, mixing with the other hot water of the shower as he continued to rut her right through her climax. Twilight continued to cum as he fucked her even faster. He felt his own orgasm coming on like an unstoppable train.

"Twilie!" he cried as he slammed it home one last time. She came again even harder as she felt him swell inside her, his flare stretching her to her limit, pressed against her cervix. She felt his cock pulse and throb inside her as his began to fill her with a torrent of his hot seed. It felt like drinking hot cocoa too fast. The warmth of the liquid radiated from inside her. And there was so much. She tried to step away, but his hooves were wrapped tightly around her, holding him in place. The remaining soap helped to aid her escape and she wriggled free. He slid out of her with a wet 'plop', even as he continued to cum. Twilight turned around quickly, intent on getting a taste.

"Gah!" he nearly shrieked as he felt her mouth on his dick. He gave her one last mouthful before he became too sensitive to let her continue. He pushed her away and they both slipped and fell onto the tub floor together. Shining landed on his back, and Twilight landed on top of him. She just laid there and focused on his flavor while just enjoying the warmth of both the water on her back, and him, panting under her. She reached behind her and turned off the water. Finally she was able to cast her contraception spell. Hopefully it wasn't too late.

"Wow," she gasped.

"Yeah," he agreed.

"We are doing that again!" she said.

"Shit! What about Cadance!?" Shining realized. His post-coitus sobriety hit him like a bucket of ice water. "We can't be doing this if Cadance is here. We'll get caught!" Shining quickly got to his hooves and finished washing up. He gave her the soap and stepped out of the shower, quickly toweling off.

"Relax," Twilight assured him. "She went upstairs to bed earlier. She's probably in a deep sleep by now. "

Upstairs, Cadance clopped herself silly as she pressed her face into Night Light's pillow, huffing his scent as she came yet again. She was thinking about when Night Light would come home and she would feed him her special brownies with the virility potion baked in. Her pussy dripped on the bedding as her infectious love magic continued to radiate off of her horn, out into the rest of the house.