Hidden in the closet, the siblings' breath hitches as they lock eyes, the weight of their taboo desires hanging heavy in the air. "Fuck, fuck, fuck," she whispers, her hand creeping closer to his crotch. He's rock hard, straining against his jeans, and she can't help but lick her lips in anticipation. Their hearts pound as they finally give in, hands exploring, clothes falling away, until they're a tangled mess of limbs and fucking, their muffled moans and the sound of flesh slapping against flesh filling the small space.