With a swift motion, the brother spreads his sister's ass cheeks, revealing her most intimate secrets. He runs his tongue along her ass crack, tasting her, preparing her for what's to come. She squirms, her moans muffled by her own hand. He teases her open hole with the tip of his cock, her body tensing as she takes him in inch by inch. "You're so big," she whimpers, her ass stretching to accommodate him. He grips her hips, pulling her back as he thrusts forward, their bodies entwined in a dance of taboo pleasure.