"Got a secret... can you keep it?" whispers the sister, her eyes locked onto her brother's crotch. They huddle together, the weight of their shared secret heavy between them. The brother's cock twitches, growing harder as he takes in his sister's curves, her nipples evident through her thin shirt. She reaches down, tentatively touching his bulge, her breath hitching as she feels his size. He groans, his hips bucking slightly, as he imagines her tight pussy enveloping his cock. They're both lost in their fantasy, their bodies yearning for the taboo, their secret growing harder to keep.