I was thinking the same thing, Parazombie!
My peeps never had problems having kids - all my families had 6 kids, but one with 5, and most of the parents didn't want kids at all.
The adoption thing, though, I think happens with parents who like kids.
I had adoptions on other families and now I'm thinking of looking if they wanted kids or not...
Let's go research...

oh oh - just opened the game to find out that the information about wanting or not to have kids is not on the family tree...

I'll pay attention to that from now on.