I had this issue just backwards.A chick who turned out to be male who grew up around Ducks now not only breeds his hens,but duck hens as well,and even communicates with them.
He is very hormonally messed up.Some waterfowl are like that,they just can’t control themselves.I would Seperate him for a long time and keep him in the muscovies in the same pen for about a month,or atleast until you notice him breeding them quite frequently.