We all know his "wife" is a man. So is it so much of a stretch to consider that Chuck might actually have a vagina and XX chormazorms? Remember, when a vagina-haver takes man hormones they turn indistinguishably into a man, and you can't really go back. The other way isn't true though, because you'll never really look like a woman once those mannish secondary sex characterists develop, like brow bossing for example