You talk about only mom you would say "her kids are great" or dad and "his kids are great" You have to go out of your way to discuss mom and dad in the same breath and then say "take HER kids away". There is a gender bias against men but somehow I think people will believe acknowledging this will deflate the womens movement.
You have to go out of your way to consistantly refer to the kids as "hers: and not theirs. In and of itself, no biggie. But it perpetuates the problem of the bias