The Ladies Club (1986)

A young boy walks in on his topless sister only wearing panties in her bedroom. She asks if he ever knocks and he says how else am I supposed to see topless women? She doesn't try to cover her breasts as they talk. She's deciding what to wear and he says she makes everything look good. She says he's just awed by the site of her tits. He says if only you weren't my sister and tries to hug her, but she pushes him away.