Her brother Tom, inside Mary

"Fuck yes!" Mary shouts, completely oblivious to the two visitors.

"Woah..." you say. "How did..."

"I don't know," Julie says then kicks the door shut. Her hand grabs your fly's zipper, and your hastily stuffed cock flops out again. "But I say we finish what we started."

Your blonde beauty of a sister pushes you into the nearest chair and squats down, taking your whole 7-incher down her throat. You moan, then your eyes wander to find Mary again. Your girlfriend, her tits bouncing and her eyes glazed, is bent over one of the armchairs of the couch, and with her pussy stuffed with her brother's cock.

"Shit sis," her brother Tom says through gritted teeth. "Your pussy's so fucking tight!"

"God your cock is so big..." she replies.

"You fucking love big cocks, don't you sis?" Tom groans. "Even... oh god, even if it's me!"

"I just saw my boyfriend and his sister doing it..." Mary gasps. "I had to-- oh!!"

Mary finds your gaze and her eyes go wide at the realization. Her brother is still out of it, blinded by wet pussy, but she sees your sister deep-throating you while your stare drills into her eyes. She mouths your name in disbelief, but you mouth hers back, then grasp your sister's hair. Mary knows that sign from every blowjob she's given to you, that your cum is about to be rushing into her stomach. Mary suddenly arches her back, bending toward Tom and grabbing the back of his head.

"Sis, I'm gonna...!"

"Fuck Tom!"

You know that sign. Mary is going to cum. And cum hard.