Emma ups the ante to anal.

You all get right back to business, brains rewired for only one thing: more sex. You're all sharing freely now, like good little orgymates. Franklin plows his sister from behind while you introduce your still-hard cock to her mouth, still dripping with cum. As he fucks, Franklin fingers your girlfriend and sucks on her juicy titties. You tell him all her favorite moves, especially biting her nipples, and Emma starts to sway and lose herself in heat. Franklin's cum mixes with yours as he finishes inside Beth and pulls out, dripping onto her sticky ass. Emma leans over to start tonguing huge globs of cum out of Beth, and even gives her asshole some attention. All of you are completely nude now, sweat shining in the lantern light, like cavemen following primal instincts. Emma crawls over to you and starts to worship your cock.

"John, you haven't fucked me in the ass once today. I need your fat cock to fill me up. Please?" Beth is blowing Franklin when she sees that Emma is upping the stakes again, and watches with envy as Emma squats down on your monster and takes the entire thing up her asshole. Franklin sitting cross-legged, promptly picks her up and holds her in front of him, putting his gym physique to good use. He sets her down in his lap, lapping at her succulent breasts as he does so, then spits on two of his fingers and starts to rub them against her puckered anus. Emma is starting to cum again as he slides another finger inside, then another. Beth is so turned on and lubed up with hot cum that she's ready for anything. She squats on the balls of her feet and orients her tush against Franklin's stiff erection, then, without ceremony, jams herself down on top of it. She and Franklin both cry out, and she melts into his arms as he slowly draws out and thrusts back inside of her. Despite being a nasty, taboo-breaking brother and sister who are covered in all kinds of bodily fluids and taking part in a marathon of shameless sex, they look like a romantic couple. You pull Emma close for a cuddle and you both bask in their adoring radiance.

"Oh, doesn't that just take you back, Emma?"

"Our very first time assfucking. It was so romantic, wasn't it, John?" They are truly beautiful together. Beth and Franklin are starting to get tender and amorous, even lovey-dovey. They're even using pet names from when they were still kids.

"Franklin, do you think I'm beautiful?"

"Oh, Ellie, how could I not? How did you get so cute? How did you get so wonderful?"

"Just using what Mom gave me, I guess. I love you, Franky Panky."

"Oh my God, what would Mom think of us right now? Seriously." At the suggestion, Beth snorts thinking about her mother's inevitable reaction. Emma speaks up and throws in her two cents.

"You should invite her next time! I love it when my mom and I fuck together, it's been so good for our relationship." Emma seems so earnest, like she's just a gal pal offering relationship advice.

"Are you shitting?" Franklin laughs. "There's no way she'd go for this." He starts to buck his hips more as Beth nibbles at his ear and strokes his back. Emma offers more encouragement.

"Show her that you guys are getting along so well now. Make sure you get more physical with her, too, more hugs and kisses whenever you see her. If she asks why, just say it's not strange for people to show affection to their parents." Emma coos softly as you stick your cock back in her ass again and start fucking.

"Just find -oh- a place where you can all be alone -mmmmMMMmm- and see how far you can get -AH- and make sure she's as horny as -hnng- possible before."

Franklin and Beth are picking up speed now. Every time his cock slaps up against her she takes a sharp breath and her lovely tits bounce in a way you're sure they never have before. You keep fucking Emma in the ass as you and Franklin slowly synchronize rhythms. You lock eyes with him for a brief second, all you need to confirm that you're both about to cum again. In perfect unison, you both pull out of your chosen fuckholes. Beth and Emma flop into the middle of the tent as you and Franklin shower them with tangy gifts from above. The cream gets all over your heavenly ladies, who are looking almost oiled up as they slide around on the now-slick floor of the tent. Beth holds her hands softly to her face, feeling like her skin is being nourished by your seed.

The night passes in a whirlwind of desire. Emma takes Franklin's cock again and eats Beth's pussy, sticks a finger in Franklin's asshole and teaches Beth to tongue him. Just as midnight rolls around, you hoist Beth into the air and start to fuck her pussy, both her legs flexibly hooked over your shoulders, arms around your neck like a romantic fool. Emma, playing dirty matchmaker one last time tonight, shoves Franklin up against his sister's backside where he introduces himself to her anus once more.

"Two-- two-- two huge--" Beth can hardly form words anymore. She shuts her eyes and buries her face in your chest as you both give her all your remaining ****. Droplets of sweat fleck off of her nubile body as you pound faster and faster. A lesser girl would be torn apart by your length and his girth. Emma is busy desperately rubbing her clit, watching this magnificent scene play out before her. Suddenly, Beth throws her head back and screams to the sky.

"Thaaaaank youuuu! Oh, thank you, thank you, thank you! My brother! My brother is fucking-- fucking my--! My ass!" You feel a hot trickle on your stomach and realize that she's squirting. You and Franklin both completely empty yourselves inside of Beth. Your cocks, both finally spent, limply flop out of her holes and let the hot spunk drip out onto the floor. You all collapse in a heap on the floor, breathing heavily as one. Franklin strokes Beth's hair and tells her he'll always love her, just like a brother should. You all fall asleep together, entwined in one another's arms.