Yeah, By Total Accident

"Mia, sit on your sister's face like a good little sister and we'll be alright." Ryan ordered. Mia paused and stepped forward, still clutching at her sex.

"No. If you got us pregnant, we could be together forever. We could fuck every day." Her mind rattled on. She was so close to Ryan, but he did not flinch.

"Mia, this time... we should not choose for Claire. If you **** this on me... Hell! If I have a fucked up **** baby with you, I will not fuck you ever again... If you do this. We clear?"

Mia froze, shaking at the prospect of losing Ryan. She whimpered like a tortured puppy, "But... Why? Don't you love me?"

"I do. This is love." said Ryan. "Don't you see what this whole game has been doing? It's been pitting our interests and desires against each other. We've gotten away with so much at the expense of each other. Maybe we all won a bit in some ways. I've gotten more than I could ever expect from a Saturday night. You too." Claire and Mia both nodded. "Now though... the game is almost over... and we can do whatever we want afterwards. We can choose whatever we want. This game has taken us all out of our comfort zones... changed us a bit. But this decision, maybe we can't take back. And it's a decision that will change our lives forever." Ryan looked at Mia as she peered through her eyebrows, dismayed but understanding. A single tear fell from her eye and he felt the need to comfort her. "So, let's choose to do what's right for us... as a whole." He smirked and then pulled Mia into a hug to remind her that everything would be okay.

"Fuck!" He shouted through gritted teeth as he felt his body fight against him. His hands moved down to Mia's ass and lifted her off the ground. He could feel blood pushing its way into his cock, inflating him like a balloon, until it stood at full attention and then he brought her down onto his cock like a piston. Mia's pussy slid down onto him like a perfect glove, moaning as her entire body was shook by the feeling she had craved for so long. His hips slammed against her and her ass shook as he **** himself all the way inside. He pulled out with all his might, but was **** back into her over and over again. He fought valiantly against his own mind and muscles to no avail. After several thrusts he let the box take over and stopped trying to stop his body from fucking his twin sister. It was inevitable now, might as well enjoy it.

Claire rolled her eyes and watched as they hammered it out in the middle of the living room. She could see the conflicting emotions in her brother's face. She could watch him fight against his body... and she knew the control the box had on him. "You love-able dumb fucking idiot."

"I'm so sorry, Claire." He moaned between frenzied panting thrusts.

Liquid dripped from their crotch and spattered over her as she responded. "I know, you dumb turd! You're a real idiot, you know? Who would have thought it was your compassion that did you in?"

"I know." He responded. "I'm an idiot."

"Ssh." Said Mia, "Just fuck me! This is amazing." She rode against him with all her might and kissed him like she never wanted this to end.

"Yeah you fucking are," Claire said, watching her twin siblings engage in the most relentless sex she had ever seen. They were like a machine. "You better fucking enjoy it!"

"I will..." he said. And he meant it. Then Ryan noticed, he could move himself... and he could enjoy it. As long as he was working towards impregnating Mia, he could do whatever he wanted. He fumbled slowly towards the wall as he fucked his sister. His arms burned after a few minutes, but he couldn't stop.

Mia kept moaning, "Grow Penis Grow," as he pounded into her. Each time he thrust and his penis expanded inside her it felt like more and more of Mia was one giant flesh light, built for his pleasure. Now he slammed into her, using all of his might to heft his penis. Mia's organs seemed to shift around the massive bulge he put into her. She only stopped as it was getting hard to breathe as he rearranged her organs. Mia stared down at her body being contorted in pleasure. "That's so fucked up, but so hot."

Ryan couldn't stop pounding into her, but could feel his arms getting tired after several minutes of hefting Mia and his now massive cock. "I've gotta put you down Mia."

"Do it on me." Claire said. "I don't mind watching, but I would like to be included since this is the way it has to go."

Ryan continued thrusting and felt all of his muscles burn as he dropped Mia on top of her sister. Now he could feel the mass of them move as he thrust into Mia's wet and stretchy pussy.

"Can you turn around, Mia?" Claire asked? "I would really like to be here with you... knowing what's going to happen."

"Fuck me! Not while I'm being pounded so hard. It's so fucking gooooooood." Ryan could feel her pussy tighten around his cock as she came and she rag-dolled into Claire's bust. When her wits somewhat returned, she said, "That was the best orgasm ever. More of those please."

"Here. Maybe I can..." Ryan said, as he attempted to switch to Claire. It seemed the box was okay with this. He pulled out his cock and shoved it hard into Claire, but his cock was so big by this point only his tip could shove in.

"Fuck. You're stretching me too wide. It's too... big." Claire gasped as Mia rolled off of her and re-positioned facing her.

Ryan's cock looked gargantuan and for too large to fit inside of Claire. Mia wondered what her holes looked like and briefly considered shoving a hand in her pussy to see, but quickly realized that Ryan could not stop and her pussy was the only solution. She straddled her sister and shouted, "Fuck me, Ryan." Mia had wanted this, but did not plan to hurt Claire. Ryan remounted and shoved inside his twin, forcing Mia's lips to form an O.

"How big did you make his cock?" She said, thankful to not be fucked by that monster, but worried of what the future held.

"Really." Said Mia, gasping as Ryan renewed his onslaught. "Sorry."

"Mmhmm," Said Claire. "Just kiss me." She again felt like the adult in the room as her stubborn and stupid younger siblings fucked like rabbits on top of her. She had come to terms with the strange sexuality on display, the taste of her sisters tongue, the feel of her tits as they rocked and smooshed against her sister's tight body, and even the burning desire to be filled again by her brother despite the fact that his cock now might not logistically fit at all and if she had any say over her body after this game ended, she would surely take Plan B at her soonest convenience.

Mia came again as they made out. Their lips were tender despite all of the thrusting that jostled them around. Claire could tell that this is everything her sister wanted since she took that card, but also one of her deep desires since she found out she was sexual in the first place. Maybe this was okay after all. Claire would rather be orgasming as well, but her sister's embrace was enough.

"Fuck! I'm gonna cum." Ryan announced like a bull horn.

"Yes!" Mia squealed.

"Fill us both brother," Claire hinted, worried that any subsequent fucking would be painful.

Ryan groaned as he felt his cock pump inside Mia, fulfilling almost all of his wet dreams. After a few shots he hoisted his penis out and against Claire's entrance pumping her full of copious amounts of jizz as the prior deluge squeezed out of Mia's pussy and onto Claire's. Burst after burst filled up Claire until she too was dripping from her snatch. And when he stroked the remainder of semen out of his lengthy shaft he spoke, "I gotta say, I might miss the size of these loads."

"Me too, actually." Claire chimed in, wishing yet again that she could be fed semen.

Mia obliged her as the bell dinged and Ryan waddled over to the box, dripping dollops of cum on the floor as he went. He glanced at the card as the top spun. "Woah... nice."