>>281238796
They never say that the brother is drawing her. Ryou just responds that she uses mirrors and photographs (which is very common).

Also they directly establish afterwards that she and her brother have different styles, so clearly he isn't the one drawing the nudes.

I can absolutely accept that one might think that he helps her take the photos, but to think that 1. She's fully nude in the photos and 2. That they're fucking, is just a huge reach IMO