The air is thick with tension and unsaid words as the siblings lock eyes. The brother, unable to control his lust, reaches out, running a hand over his sister's round ass. She stiffens, then relaxes, pushing back slightly. He takes it as an invitation, grabbing a handful of flesh, feeling the softness. She lets out a soft moan, her breath hitching as he squeezes harder. He can feel her heat, her desire, and it spurs him on. He leans in, his lips finding her ear, "I want to fuck you, sister. I want to fuck that tight little ass of yours." She shivers, her body betraying her, wanting the same thing.