You won't see any "transgender" in a medivial fantasy setting... Never.
Its either gender bender or crossdressing, transgender isn't a thing in a medivial era.
It's not Yuri. If he hides and pretends to be a girl than no one will know he's the heir to the dukedom. So no one will try to murder or assassinate him. It's a trope thats been used before and I presume even happened in real life in the past.