Let's keep in mind these words when we address your questions.
I only said that I support children being allowed to draw their families, whatever their family dynamic may be, if that is the assignment. Other than that I don't understand the question. Different children are going to have different drawings. If a child lives in a household like my grandson does, with a mother who isn't going to shy away from teaching him actual human anatomy (she's currently in nursing school), he might very well draw naked people given that assignment. Children are unpredictable.
No I don't. I think it's natural for children to grow more curious about their bodies as they get older. Also I don't think there's anything boys draw more than penises. Not Pokémon, not Goku, or whatever, it's penises hands down.
I would encourage you to provide evidence this actually happened.