With the engine purring and the wipers swishing, the siblings' argument escalates, their voices raised, bodies inches apart. The brother's hand finds its way to his sister's thigh, tracing lines of heat as they debate. She gasps, her breath fogging the windows, and he takes advantage, kissing her deeply, his hands roaming her curves. In the tight space, they fuck passionately, her tits bouncing, his cock pistoning in and out, their moans drowned out by the rain, until they both climax, bodies shuddering, leaving them breathless and sated.