Turns out your girlfriends brother sister roleplays aren’t just games. She wants to watch the real deal. They devise a plan to get you to take your sisters virginity. Your girlfriend ties you up and acts like shes going to fuck you when your sister walks in. You have no choice, your cock gets hard as soon as she starts sucking it. You stare in shock at your girlfriend while she just watches you get fucked by your sister. (End clip where sis finds out shes pregnant!)
