I am normally pretty boring and have 2 kids, but I am exploring the game further. I currently have 1 toddler, 1 infant and a baby on the way. Enjoying the family play.
I'd say 66% of the time it's 1, 33% it's 2, and very rarely more than that. I don't think I've ever had more than 4. And that was because surprise triplets happened.