Your sister???

There on the bed with her legs spread and fingers already at work on her own clit, is your sister. Oh god, what is your sister doing there? What are the odds that your girlfriend would pick your sister?

Katie has never met your sister, so it is no surprise that she wouldn't think twice about picking her. She has the same hair and eye color as you, but she is rocking a pair of D's that is currently jiggling at you through a pink lace covered bra. Her stomach is very muscular, and appears to be slick with sweat.

With the hand that isn't currently rubbing herself, she gestures your girlfriend to come over to her. Katie obliges and starts slowly pulling off all of her clothes as she walks towards the bed. Your girlfriend apparently forgot you were there, becuase she haphazardly pulled her panties down and chucked them across the room. Thankfully you saw it coming and managed to grab some pubes on her balls to hold onto. Which was probably a mistake, because your girlfriend was currently guiding her cock into your sister, and you were about to be pinned against her by your girlfriends balls.