With kids, I spend all my nights and mornings with them. I do sneak in some work at 4 AM or so.
With just my wife and no kids, I spend all nights and mornings either dating her or playing games.
Being single, I'd spend all my free time on dating and arguing with strangers on forums.
It doesn't really change much. Arguably I get more work done with kids, because I need some escape from them.