How is this even in debate? Of course boys learn how to be a man, to a significant degree, by observing their father (not emulating, but observing) and girls by observing their mother.

I think there's a tendency for people to underestimate the exposure they get to their families as compared to the exposure they get to anyone else in the world when it comes to close emotional contact.

Some of use who are aware of having had emotionally withdrawn fathers (or mothers) realise this better than others.