Water cascades down their bodies as they stand close, too close, in the tight shower space. The brother's cock twitches, pressing against his sister's hip. She bites her lip, feeling the heat between her legs. He reaches out, tentatively touching her breast, feeling her nipple harden. She gasps, her hand finding his cock, stroking it gently. They're enveloped in steam, their bodies sliding against each other, hands exploring, until they're consumed by their taboo desires, fucking hard and fast in the pounding rain of the shower.