You have always had a sneaking suspicion your sister is a slut, but you've never had any proof. That is, until today when you caught her scrolling through porn on Reddit. Fucking whore! You decide to take what she is clearly baiting to get, and so you push her down on the bed and expose her tits. You suck her titties and then push your dick inside her mouth. She protests but she takes it and your suspicions seem to become more and more validated. Finally you start fucking her and her pussy is soaking wet, as she takes your dick. She begins to like it, and when she starts riding you she's fully into being used by her brother, like the whore you knew she was. She cums on your cock, no surprise there, and then you flip her over on her back again so you can fill her pussy with your load while looking into her cute, slutty face. Job done, she got what she was asking for...