Oh wow, I'd take a guess and say maybe the new addition is bringing up sad memories for him. The poor guy. This is perfectly natural and normal though and something he might be trying to work through on his own. He might not want to upset you.

From the other things you wrote, it sounds like he is totally on board otherwise.

One thing - no matter how many children he has already, or how many he has seen born, it will NEVER, NEVER get old. Please don't worry about that, why do you think he went through what he did after the reversal - to do it all over again, cos it's so darn great!

xoxoxo