In the cramped, dimly lit bathroom, the siblings' breaths mingle, heavy with lust. The sister, just 16, her body still developing, presses against her brother, feeling his hardness. He's 18, his cock thick and long, tenting his jeans. She reaches out, touching him, and he groans, unbuttoning his pants to free his length. She licks her lips, eager, and he lifts her, impaling her on his cock. She's tight, so tight, and they fuck, their bodies slapping together, their moans echoing off the tiles, until they both come, hard and intense.