From the web site:

"I always think of my sister wet. Always have, seeing her come out of the shower with a little towel around her and her hair tousled, I'd think, that's my sister, that's what she looks like under it. Long before I knew this was sexual thinking, I imagined her nude, unchanged under all the vast variety of clothes she wore. As I saw her discard clothing, I was more convinced of my mental image of a single naked sister under it all."

Sis is reading  mags in the dining room. Bro lends her a hand (and other body parts).