As the the proud father of two young boys I feel inclined to quit whilst I'm ahead. My wife semi-jokingly says that she would like a third child if she could be guaranteed a girl. My argument for not pursuing this "opportunity" is that there are quite a lot of all-male siblings in both sides of our extended family and therefore the chances are we would have another boy.

With the recent news from the Beckham household too, I wondered if there was any genetic basis for this?

Finally, what would be the evolutionary advantage of single-gender family units? The benefit of accumulated parenting experience with one gender?