In the dim light of their shared room, siblings succumb to their forbidden desires. She straddles him, her panties soaked, as he grips her hips, his cock straining against his boxers. They kiss, tongues entwined, as she grinds against him, her wetness seeping through the thin fabric. They're close, so close, when a sudden knock at the door freezes them, their hearts pounding with guilty longing.