I've noticed already a number of players choosing female sovereigns, because it's easier to find a mate and get one's dynasty started.  I've had games where, as a male sovereign, I've never encountered a recruitable female.  However, choosing a female to avoid this seems kinda cheesy, and is likely to become the standard play because of the advantage.  To offset this and make choice of sex less lopsided, I suggest a period of pregnancy prior to the birth of a child, during which the character would be greatly handicapped, e.g., halving all their stats for a certain number of turns.