Normal for anyone with an older brother? Yes! Or two younger ones, as I had.

I especially appreciate your bringing up that aspect: In an early draft I mentioned my brothers and that the kind of roughhousing Harry describes was normal for them--NOT the kind of thing that needed to be brought to the attention of Child Protective Services. I cut that for space but think anyone who comes from a family of two or more boys will nod in sympathy with your point.