Ok, I expect there'll be people noticing Twisted Hiccstrid one shots have been separated out and uploaded individually! Basically, technical issues. It can't make that much difference to you guys where they get posted.

Prompt: Hiccup and Astrid are biological twins (non-identical, obviously). They've been together/having sex since they were fourteen, and still are as adults. For a plot twist? They get caught!

Because of the obvious resemblance between Hiccup and Valka, I can't really change his mother, but since Valka and Stoick would never come together and create someone who looks like Astrid, there will be a different (oc) father.

So... on the topic of warnings, beware the incest!

-HTTYD-

Soft footsteps sounded outside his door. Hiccup sat up in his bed, watching the door slowly open and Astrid's face peered around it. She beamed upon seeing he was awake, stepping into his room and closing the door behind her. She had on a soft blue dressing gown that Hiccup hoped she had nothing on underneath.

He revised that opinion when Astrid untied the belt, shedding her gown to reveal she had on a corset, tight on her already slim waist and hips, and pushing her breasts up together to give her a cleavage that could kill. The cute little scrap of lace hugging her hips that could hardly be called underwear was just as alluring.

"Wow. Is it my birthday?"

Astrid crawled up his bed, the view of her plush breasts unavoidable but then he was really rather enjoying it. Her mouth pressed against his jaw, trailing up the sharp bone there.

"Well if it was, it would be my birthday too. And it's not."

"It's almost like we share a birthday."

She smirked, blue eyes lit up.

"We share a lot more than that H."

She kissed him soundly, nuzzling his cheek cutely.

"A house."

Kiss.

"A bed."

Kiss.

"Parents."

Kiss.

"DNA."

Kiss.

The two were so much more than just lovers - they were blood, siblings, brother and sister. Twins. They had been born together, even resided in the womb together. Their whole lives had been a joint effort...

Who else was Hiccup going to fall in love with?

Astrid had, luckily, felt the same. That first awkward kiss when they were fourteen, slightly tipsy on their first brush with alcohol, had at first seemed like a huge mistake. They'd avoided each other, pretending it hadn't happened for weeks. Then one night, Hiccup braved going to Astrids room in the dark and they talked. Talked and hugged.

And kissed.

Mostly talking.

At first.

Once they had gotten past the awkwardness and admitted to their mutual, illicit and illegal and incestuous feelings of desire for the other, they hadn't seen much reason not to be kissing. Whenever they could, at first only in the dead of night and when their parents were out.

Over time, Hiccup and Astrid had become bolder, kissing sometimes with their parents in the next room and fooling around frequently while one or both parents were home.

Hiccup had insisted they be alone when fooling around became more. Astrid had taken his virginity and he hers, losing their innocence in every sense of the word to their twin. If only because Hiccup knew it would be addictive, and it was - they'd barely stopped since. Nobody could know, obviously, but both Hiccup and Astrid had accepted that.

Astrid nipped his lip, pulling Hiccup from his nostalgic reverie. Her tongue invaded his unresisting mouth, those gorgeous breasts practically shoved in his face as she straddled one of his legs. Hiccup ran his hands over the corset, the texture pleasant to the touch and he hummed against Astrid's lips. She broke their kiss and effectively shoved his head between her breasts, letting out soft sounds of pleasure when Hiccup littered kisses over all the skin he could reach there. He could feel Astrid's lace panties were damp against his bare thigh - Hiccup often only wore shorts to bed - and reached up to squeeze one plush mound through the corset. She moaned a little louder and Hiccup regretfully pulled his head out of the heavenly place it had been.

"Remember, we can't be getting overheard."

Astrid nodded, frowning. When they were alone, Astrid could be uninhibited and vocal about her pleasure but their parents were home, so they had to be quiet. Hiccup brushed his fingers down across the front of her underwear, just catching the edge of her sensitive little clit and Astrid shuddered, whimpering and bucking her hips to silently demand more.

He continued rubbing her clit through the fabric, Astrid's lips catching his hungrily to muffle her cries in their kiss, moaning into his mouth and Hiccup thrilled in it. Her damp lace grew wetter, hips pushing against his hand for more of the pleasure Hiccup's fingers gave her. He hungrily watched her shake, felt her nails sink into his skin and Astrid bit her lip to quiet her moans as he successfully brought her over the edge.

"You're so hot when you come."

"Mmm. Get your pants off."

Hiccup happily complied, dropping his shorts and letting his cock spring free. Astrid eyed him hungrily, beckoning him closer to remove the corset; it was hot but she couldn't fuck all that well in it. Hiccup ran his hands over the satiny material, then began to unfasten the back with practiced hands - it was her favourite corset and he was as skilled as anyone could be at getting her out of it. He kissed her neck as he worked, leaving Astrid squirming pleasurably and gasping softly.

When he peeled the corset from her body, Hiccup immediately had his mouth on the revealed skin, sucking at her swollen nipples until Astrid was writhing and whimpering. He added a teasing hint of teeth to make her shake, succeeding beautifully and Astrid fisted a hand in his hair, hauling him back up to kiss him him roughly. He slipped her underwear off, rolling on a condom while Astrid made herself comfortable on his pillows.

Her hips lifted slightly so Hiccup could position himself and slip inside her with ease, both biting at pillows and each other to quiet the groans of contentment that they were finally joined again. Astrid rolled her hips to test the angle, purring happily and Hiccup almost came from that sound alone. Hie moved slow and sure, knowing how best to arouse Astrid further, kissing along her collarbone and neck until she growled in frustration.

"Cover my mouth and fuck me properly."

"You sure?"

Hiccup didn't love doing it because he craved Astrid's vocalisations, but sometimes it was necessary. Astrid nodded, craning her head and kissing him before his hand splayed over her face. She nodded to say she could breathe, arching her back and moaning into his palm when Hiccup began thrusting harder, faster.

He bit lightly at her throat, focusing on giving Astrid the fuck she asked for and loving every second as she thrashed and bucked, scratching his back and biting his palm when he pressed his hand a little too firmly. She felt incredible on his cock, taking her brother perfectly with her soft, welcoming heat and squeezing her muscles around him to hold him deep inside her.

Astrid's nails sank deeper into his back, tearing skin as her back arched and her thighs tightened around his hips. Hiccup knew when she was close, continuing to thrust into her at the pace she was responding so beautifully and erotically to, the passionate heat of her reactions threatening to send him over the edge.

His hand slipped as he came, Astrid's last few moans full volume but both were far too distracted to notice as they shared in the climax with their twin. Gasping for air, Astrid's breathing was ragged and damp on his shoulder where she leant up, embracing him.

"Love you."

That was often the first thing out of her mouth when they were done, and Hiccup's response was equally as predictable.

"Love you too."

They kissed lazily, nuzzling and stroking each other affectionately with soft smiles.

At least, until Hiccup's bedroom door flew open, revealing their close, naked bodies to their parents.

Not good.

Their shock was obviously huge, stilling them long enough for the two to grab pillows and attempt to cover their nudity but the damage had been done; Hiccup still had a condom on for Thor's sake.

"I would ask what's going on but that is disgustingly apparent. Get dressed, both of you."

Hiccup had to fight not to wither away and die under their fathers glare, their mother not even able to look at them. Hiccup didn't really blame her. As soon as he turned away, both twins crawled toward their clothes. For Astrid, that was only her discarded underwear and the dressing gown across the room. Hiccup handed her a t-shirt from his pyjama stash next to his bed, putting on one himself and feeling no less exposed even when he had his boxers back on.

They looked at each other, sharing a nod that carried no words but a potent message.

We aren't denying this.

"Dressed."

"Good. Come with me."

Hiccup stood up first, picking up pyjama bottoms and stepping into his slippers, wary to approach too close to his parents and distracting them while Astrid hid her discarded corset. Best not to scar their parents any further.

He watched as their father sat at the table in the kitchen, holding a glass full of more than a double whiskey. The alcohol scent on the air was strong. It was hard to look at their father Ashton, with his blue eyes and blond hair he was the mould Astrid had been made from while Hiccup was the spitting image of their mother Valka. It was like seeing he and Astrid look disappointed in themselves and each other.

"I don't even know where to start."

Hiccup stood with his hands at his side, eyes downcast as he waited for whatever was coming. He couldn't meet his mothers eyes. Somehow her silent sadness was far worse than their fathers anger. Astrid made it downstairs then, shamelessly walking up to Hiccup and taking his hand. Hiccup let her, squeezing her fingers in return.

"How long?"

The words were quiet, strained, resonating with anger. Hiccup still wouldn't lie, not about Astrid.

"Since we were fourteen."

"F-fourteen?"

Valka's words were different. Heavy with tears, disappointment, confusion.

"We didn't just jump straight into bed, but... yeah."

He could feel Astrid shaking, despite trying to stay stoic and come across confident. Acting on instinct, Hiccup pulled her closer and wrapped his arm around her shoulders. She always looked so sweet in his t-shirts, the way they hung down to her muscly yet satin-soft thighs.

"Don't touch her!"

Hiccup glared, tightening his arm as Astrid did the same around his waist.

"We're not kids. If you don't want us here, say so and we're gone but you aren't going to break us up."

"Broken up? You should be locked up!"

It was already clear to Hiccup that now they had been caught, they had to leave.

"Have me locked up. It won't change the way I feel about Astrid."

"Goes for me too."

Unlike their parents, conviction and strength was the outstanding tone in both their voices.

"You're right. I want you out of here. If I have to look at you much longer I'm going to be sick."

They had expected that. They had prepared for it.

"Alright. We'll be gone before you know it."

Hiccup didn't manage to look his mother in the eye, terrified of what she would find there. Holding Astrid's hand, he led her away from their parents, up toward their rooms.

"Better pack what you can. I'm calling Dagur."

Astrid nodded, leaning up to kiss him and it was as much a question as it was confirmation - were they still ok? - and Hiccup answered it with equal passion.

"Go on."

Hiccup grabbed his phone as Astrid headed to her room; both had their clothes separated into essentials, had boxes and bags ready to pack. They had always known it could happen. Mentally apologising as he pulled up the contact info, Hiccup hit 'dial' on Dagur's number.

"H? What's up?"

He answered almost immediately, to Hiccup's relief.

"We uh, we got caught."

"Oh man. My offer still stands. I mean the spare room is nothing great but its yours if you need it."

Hiccup thanked his friend vehemently, apologising for the late hour again. Dagur waved him off, insisting he was still up after getting back from work as a security guard. After hanging up, Hiccup began piling his clothes into boxes and bags. Not one for high fashion, Hiccup had that and his art supplies packed up in short order. His shoes went into a duffel bag, and his books and laptop went into a box.

Bathroom supplies... Hiccup dressed himself properly and checked if he needed anything that was left behind. Nope. Having kept an ear out, Hiccup knew their parents were downstairs probably aggressively discussing their childrens relationship. So he felt quite safe to leave his packed up room, heading down the hall to Astrid's.

She tensed at first footsteps, but relaxed when she felt Hiccup slide arms around her waist, pressing a kiss to the side of her jaw.

"We good?"

"We're good. I'm packed up. Think I'm sacrificing my DVD collection downstairs but hey, that's replaceable."

Astrid actually giggled, turning around to kiss him again.

"Got your 'proof of' stuff for when we need to sign grown up documents?"

"Yep. Art stuff. Clothes. Bathroom stuff. I'm good to go, just waiting on you."

"Go start filling up the car?"

"Good plan."

Hiccup managed to move his things in two trips, by which time Astrid was ready.

"Should we give back our keys?"

"Good idea."

Hiccup unhooked the Haddock home key from the rings that held only car keys and his work locker key now, Astrid doing the same. Holding hands, they walked back into the kitchen where their dad was on his second glass of whiskey. Maybe third judging by his glazed eyes. They put the keys down silently, and the only thing that threatened Hiccup's resolve were the tears in his mothers eyes.

Astrid was just leaving his side to circle to the passenger side of the car when Valka caught up with them, looking harried and distressed in her nightclothes with flyaway hair tied back in a braid.

"You're really leaving?"

"Dad would have expected us to stop. What difference would that make? It wouldn't change that it happened or the way we feel."

His hands shook at his side; Hiccup hated to see his mom so upset, her huge green eyes swimming with tears. She hugged him out of the blue, and Hiccup immediately returned it. Astrid came back to share in the embrace, all three a little teary eyed when Valka stepped back, wiping her face and looking at the two stood next to each other.

"Have to say, not the double trouble I expected when I found out I was having twins."

Hiccup reached for Astrid's hand, lacing their fingers together.

"I'm sorry we're putting you through this, but I can't say I'm sorry about it happening."

"Yeah... what he said mom."

Valka closed her eyes, shaking her head.

"You should go before your father regains his vocabulary."

Feeling impossibly awkward as he tried to work out how to say goodbye in this suddenly shifted relationship, Hiccup could only shrug.

"Yeah. You uh... well you can call us if you want."

Valka nodded, stepping back further as Hiccup and Astrid got in the car, starting the engine. Dagur and Heather lived near an hour away, but the redhead and brunette waiting outside, smoking in their pyjamas on their front step.

"Hey Dagur. Sorry about the late hour."

"Not a problem. This stuff doesn't happen on a schedule. Heather even made a late dinner since we probably won't be sleeping anytime soon."

Dagur stood up, tossing his finished smoke in the direction of the empty tin acting as an ashtray, then reached inside for shoes and headed over to the car.

"Lets get you inside so we can chat."

With Dagur and Astrid both freakishly strong, they had all their stuff piled into the spare room and Hiccup had parked his car in the empty spot on the driveway.

"So what happened? Did they literally catch you in the act?"

"Yeah, pretty much."

Dagur and Heather were unqiue friends; they knew about the two having a relationship. Hiccup and Dagur had started talking on a Genetic Sexual Attraction forum online, sharing in the fact they had what others considered immoral, depraved relationships with their sisters.

Of course, Heather and Dagur hadn't met til they were adults, and were half siblings rather than twins. Dagur had been given up for adoption by their fathers first wife, Heather not by his second.

Either way, they shared a very uncommon friendship. After months talking online, they had started talking more personally and discovered they lived fairly close by. Dagur, already living with Heather, had said if it ever went bad the two had somewhere to go. Hiccup was endlessly grateful for that.

"Was it a long ragey thing or awkward silence?"

"A little rage, then told us to go. I called you and here we are. It's only temporary, we won't invade your space more than needed."

Dagur waved his hand dismissively, chewing on the cold chicken Heather had cooked earlier.

"No rush. Honestly. Get yourselves in a good place rather than just trying to get out as soon as possible."

"Thanks. Means a lot."

Dagur grinned, throwing an arm around Heather and kissing her cheek. Heather smiled, hugging her half-brother in return. It was one of those rare things nobody else understood, but at least somebody did.

The four eventually agreed to retire to bed; Hiccup and Astrid both had jobs, had work in only a few hours. They stripped down and crawled beneath unfamiliar sheets, Astrid immediately placing herself in Hiccup's arms as they cuddled up.

"It was inevitable really."

Astrid nodded, running a hand down his chest before burrowing closer still.

"I know. Guess I just kept telling myself it wouldn't happen yet."

"Me too. Get some sleep love, we'll figure this out together."

Astrid shifted, wanting to be spooned and Hiccup obliged happily, wrapping an arm over her waist and nuzzling the back of her sweet-smelling hair. Their alarms were brutal wakeups, but not nearly as much as Dagur bursting into the room in only boxer shorts.

"Morning! Oh, naked people! I didn't mean to see anything, but Heather is making breakfast so up and at em if you want the best breakfast ever."

"Mhmm. Any chance you'll let us get dressed privately?"

"Spoilsport. Sure. Coffee?"

Both groaned in agreement, then Dagur turned and bounced out of the room.

"I forgot he was a morning person."

"At least there's coffee."

The two crawled out of bed, dressed and quickly took turns brushing their teeth and using the bathroom. Then there was an admittedly excellent breakfast and some hugely welcome coffee to fuel their half-asleep selves.

"How are you both awake when you went to bed the same time we did?"

"Eh. Family trait. We're morning people. And we do yoga."

"You're crazy."

Dagur laughed, bounding around the room like he was on amphetamines, so easy to be around because nothing really phased him. Including the fact Hiccup and Astrid were twins and lovers.

"Oh, you'll need these since we all have jobs" Heather pushed two keys over to them across the table "and you'll wanna get back in."

The two took them, adding them to their keyrings. It felt alien, but welcome nonetheless.

"Thank you. Really. We would have been stuck without you guys."

"What are friends for if not for support and understanding?"

"Still. You've made the whole our parents caught us in bed thing a little easier, and that's no small feat."

Hiccup was under no illusions - their situation sucked, and it was a direct result of he and Astrid being together when nature and law and society all said they shouldn't. But they had somewhere to regroup, somewhere to sleep and eat and keep their stuff while they worked out where they were going.

And most importantly, Hiccup thought to himself as Astrid kissed him goodbye when he dropped her at work, they had each other.

-HTTYD-

Quite possibly the weirdest research I've ever done but I found several reports of fraternal and identical twins getting it on. Tops even GSA research for Adopted.