Been thinking about Leif being a transman and I think it's something he would have known since being very young, even before having to flee. As he grows older I think he would be closeted to everyone but his closest family, but in a way where others refer to him as mail and he hides himself ever being born in a female body. So most people wouldn't know he's transitioned.
He does this because the idea of being refered to as female at all bothers him a lot. I imagine also he has small breasts so this aspect is a little easier to ignore given the right clothing. However, his hair tends to grow long like his sister, so he keeps it cut (and I like imagining Nanna helping him with this).
I can't imagine Jugdral being 100% ok with transness, it would probably be a weird and confusing concept there. But then it seems like (at least cousin) incest is not as taboo there, so who can really say? Regardless, I think Leif would still fear being found out in this aspect, as he already had to live in hiding for years. And as with that he would grow to dislike that he has so many risking their own lives just for him.