In the dim light of their shared room, the stepbrother and sister find themselves drawn to each other, their inhibitions slipping away. He traces her curves, his fingers lingering on her ass, before slowly pushing a digit into her tight hole. She moans, her body arching, egging him on. He replaces his finger with his cock, stretching her, filling her completely. She claws at his back, her breath coming in short gasps as he pounds her, their sweat-slick bodies slapping together. As his cock swells, he pulls out, his hot cum coating her ass, marking her as his.