Alexandra...Your response is really thoughtful and insightful.
However, I can only respond to this from a subjective point of view, from having raised a daughter and witnessing the development of her twin boys.
She, daughter, was very dainty and demure from the start. Twin boys are rowdy, competitive and much more messy and rambuctuous than she was as a little girl. Daughter and hubby are highly educated (Ph.D) and not inclined to encourage male macho behavior. It is just there with these boys!
I don't know what to make of this other than to surmise that it is hormonal and genetic!
Patty