Probably not revealed but Mother definitely knows something. Maybe even full knows, who "she" actually is but plays along, because of the father. That would make sense ( and fitting to these kinda manga ).
Not that I dislike, just saying what I think.
It'll be so funny if this ends up like sarazanmai and after he talks it through here he's like, "phew, glad i don't have to dress up like a girl anymore! That was sooooo embarrassing " and then never wears a skirt again in his life