Busted with his dick in hand, the stepbrother's embarrassed, but his sister's intrigued. She watches him stroke his length, her eyes widening at his size. "Don't stop," she whispers, climbing onto the bed beside him. She cups her big, natural tits, pinching her nipples as she grinds her pussy against her hand, matching his rhythm. Their mutual masturbation grows intense, bodies glistening with sweat. She leans over, taking his cock in her mouth, gagging slightly on his thickness. He reciprocates, feasting on her big, wet ass and pussy until she cums hard, coating his face.