In the dim light of their shared room, the siblings sit close, their bodies barely touching. The girl's heart races as she feels her brother's thigh against hers. He's looking at her in a way he never has before, his gaze lingering on her lips, her breasts. She licks her lips, her chest heaving. He leans in, his breath hot on her neck. She tilts her head, inviting him. Their first kiss is clumsy, full of pent-up longing. It deepens, becomes more urgent. Their hands start to explore, tentative at first, then bolder. They're crossing a line, but they can't stop now. They're too far gone in their forbidden dance of discovery.