Fuck it. Go to Jenny's bedroom.

You creep to your twin's door and peek in the crack as sneakily as possible. It's hard to really see anything from this angle aside from the glow of her bedside lamp.

"I know you're there," says Jenny. "Can't sleep?" Well since you've been sprung you push the door open. You're pretty sure that the whole set up had been a trap anyway.

"Yeah I-" you start then freeze at the doorway and gawp. Your sister is laying atop her blankets naked, the erotic curves of her body presented in stark reliefs of light and shadow from the lamp next to her. And she's spreadeagle, her fingers sliding up and down her exposed lips. Her eyes are fixated on her own pussy and she dips her fingers into herself then slowly raises her hand. Sticky strings of her wet arousal stretch between her slit and fingertips and you're both mesmerised by the display.

"I'm so wet," she says, not in any deliberately seductive manner, more like she is thinking out loud. "I can't sleep either I'm just... so horny." She slides her fingers into her pussy again, collecting more of her leaking honey and plying it between her fingers, fascinated. When she finally looks up she's surprised you're still at the door. Her eyelids lower and and her look makes your already raging erection pulse. The words that follow almost bring you to your knees. "Come inside." She smiles wryly.

You swallow as you approach the bed, very conscious of your bobbing dick under your stretched shorts. Having shared a room with your twin until age 12 you weren't a stranger to sitting on her bed. Of course she'd never been naked and playing with herself while you were there, so this is a little different. Her grabbing at your shorts is also new. She rolls her eyes at your look of confusion. "Take them off," she says, annoyed at your put on coyness. "What else did you come to my room for?"

"Busted," you say as you pull off your shorts. Exposing your cock to your masturbating sister feels good and she seems to appreciate the view too.

"Mmm... this is weird isn't it?" she says, staring at your hardness as she rubs her self. You nod and start to stroke, precum already leaking out of your tip. "Do you think... dad and Betty... fuck?" She shivers at her own words and you let out a small moan yourself.

"Does that turn you on?" you ask, even though the answer is obvious. "You like **** stuff?" There's a snort from your sister and she grabs your wrist with her free hand, stopping you midstroke.

"You obviously do," she says, pulling you towards her. You're suddenly a bundle of nerves despite how turned on you are and it shows as you crawl over her. Noticing this your sister's expression shifts, slightly worried now. "What's wrong?" This was wrong isn't it? Fucking a morphed farm animal while your sister watches was one thing. Even masturbating with her in the shower didn't seem particularly serious. Actually fucking her was where you felt you would be crossing a whole different line.

"Maybe we shouldn't... go this far," you say uncertainly, which sounds ridiculous with you bearing over your sister, just one well angled thrust away from being inside her. She smiles warmly at you and slides her hands onto your hips. Her eyes drift down your body and she licks her lips.

"Think of it as my birthday present," she says softly, the quiet of the room making the want in her voice loud and clear. At this point you really don't need much more convincing but she's going all in. Jenny lifts her head off of her pillow and kisses you slowly. You moan into her mouth and feel precum drooling out of the tip of your penis and pool on her thigh. "I got you something," she whispers as you break, tilting your chin to look down her body. She spreads her lips to reveal her glistening pinkness. "So let's trade presents."

"God damnit," you sigh, whatever flimsy resistance you once had now completely disintergrated. Perfectly lined up to her spread open hole you begin to lower yourself. Groans escape both of you as the swollen, dripping head of your cock pushes past her threshold. Jenny's heat engulfs your cock as you sink into her. You swear under your breath some more. Her pussy is actually hot, almost unbearably so, making your dick throb against her molten wetness.

"OhmygodJon," she whimpers as you fill her. "Yess...oh god..." Even though you feel light headed from how amazing it feels to be balls deep in your sister, your body starts to do what comes naturally and you begin to draw your searing hot cock in and out of her. "Ohh fuck...Jon... brother... big brother..." she moans, feeling the need to vocalise her thoughts. "Big brother's cock... inside me... fucking...me... fucking ...mpphh!"

Your mouth smothers hers because you can't stand to hear her say any more. If she keeps calling you you'll come too quickly and you want to enjoy her for as long as you can. You want to make sure she gets the most out of her present. When your lips part she seems happy just to manage her breathing as you fuck her, building your speed as you work up a sweat. Having cum so much today already you seem to be doing alright with pacing yourself now. The sort of silence between you turns out to be just as hot as her earlier verbalisations though. The moans, her sharp breaths and the animal rutting sounds between you are so erotic you realise it's going to bring you hurtling towards your orgasms at any moment. But you don't want it to end so soon, you just want to keep feeling your sister's pulsing cunt around your cock forever. You see her bite her lip and it drives you to fuck her harder and she responds with soft cries of pleasure. No! That's the opposite of what you should be doing so you grit your teeth and slow down.

Jenny's breathing eases too and as she notices how stiff you are her eyes flutter open. She has her wry smile on her face that you recognize as your twin's signature look of mischief. She brings a hand up to stroke your cheek tenderly.

"I keep thinking about dicks," she says to break the silence. You want to shut her up with another kiss but the taste of her tongue would probably push you over the edge too so you let her continue instead. "Dad's dick. Your dick. Animal dicks." Your eyebrows rise.

"Animal dicks?" you say, distracted momentarily but soon realising no topic is going to help now. Anything she says is only going to make this end faster.

"Yeah like ...the bulls," explains your sister, causing you to picture Bruce the bull's thick and veiny monster. Your imagination has him fully erect now and then your sister's naked body comes into the frame.

"Oh god," you groan, unable to push the image out of your mind.

"Yeah..." sighs your sister as you continue to plough into her drenched channel. "Big bull cock and balls... Bruce fucking me with his giant thing..."

"Shit," you say as your imaginary sister's gash gets pierced by the bull's impossible member somehow and he starts to fuck her. You thrust harder.

"Mmm... I want to feel him fill me up," she continues lustily, knowing that she's in complete control of you now, enthralling you with her own fantasy. "Yeah... I want to feel his cum in me. His bull semen... just fill me up... I want to feel it." Her hands slide down your back and she grips onto your ass. She's holding you down slightly each time you bury yourself completely inside her. "I want to feel it," she repeats. "I want to feel ... the cum..."

"No..." you protest weakly. "We shouldn't... I shouldn't..." You do not sound very convinced at all, voice strained and the slapping together of your young bodies growing louder and more urgent.

"Please..." your sister pleads, her grip on you tightening. "Let me feel it...please... I want to feel it..." She kisses you again, hard and passionate. "I want to feel you. Please... big brother... please... I want you...I've always...wanted...oh..ahh! AAHH! Oh my god!"

"Fuck..fuck! Jen...!"

You're cumming and there's no chance of you stopping or pulling out even if you wanted to. Her hands hold you firmly in place as you pump your sister's pussy full of semen. She squirms against your hips, humping your pulsing cock and clutching you tightly in case you don't empty your balls completely inside of her. You don't want to miss a drop. You want to paint her inner walls and drench her through and through. To make your point you thrust as hard and as deep as you can, shooting jizz into her with a forcefullness that finally ignites her already roiling orgasm into overdrive. Her multiplying pleasure makes her cry out incoherently, almost howling like a wolf. Through the buzzing in your ears you imagine you can hear something outside in the farmyard echoing your sister's call. With one last shudder you collapse on top of her and you find your vision is swimming.

You feel your sister's warm, sticky body against you and her lips touch your neck gently. Wiping the sweat-matted hair from her forehead you kiss it before finding the pillow.

"I'm ready to sleep now," she says, caressing your chest lightly. You can only hum to agree with her as you close your eyes. Even though you can notice the glow of the bedside lamp through the corner of your shut eyelids it doesn't prevent you from quickly and finally falling asleep.

***

You wake up in your sister's bed feeling warm and rested, albeit a little thirsty. The first rays of groggy sunlight lance through the curtains and you feel a shift next to you as Jenny gets up. She stretches and yawns and it's a lovely sight to be sure. Seeing that you're awake too she smiles.

"I'm glad you had a good night's sleep. I spent twenty minutes just sitting on the toilet last night after you fucked me," she says. "There was so much cum." You sit up now, the full reality of what you did to your sister last night waking you up faster than anything else possibly could have. Your twin chuckles at your panicked expression. "I'm on the pill, don't worry," she says, giving you a reassuring pat on the head. It's only a minor comfort and you wonder how your parents or older sister would react to you impregnating the youngest daughter in the family.

"Jesus fuck," you groan, holding your face in your hands.

"Oh calm down," says Jenny, rolling her eyes. "I know how to take care of my body." She pulls the blankets off you and you feel the cool morning air hit your nethers. You of course have morning wood. She jumps next to you on the bed and takes your cock in her soft hands.

"I'm safe," she says seriously, making you grunt as she strokes you.

"Okay," you nod, voice straining. You breathe a sigh of relief as she releases you and steps away.

"Wow," your sister remarks, watching your hard cock sway in the air and your loaded balls undulate as she pulls on a shirt. "Are you already recovered?"

You look down at yourself and take stock of how you feel. You do feel replenished and surprisingly energetic now that sleep has left your system. Then your stomach growls. "Sounds like it's breakfast time," your sister announces. She picks up your discarded shorts from the floor and throws them to you.