I think it is not peculiar for a parent to feel more comfortable around one child than another as they develop their own personalities -- which is different than openly displaying favoritism. It doesn't mean you don't love them both just as much, but sometimes one child is so much like you that you but heads, as happened here. So that did seem understandable to me. And just as understandable is the feeling of guilt about this. But I think it is natural. It may not happen for every parent, it's just the how the personalities unfold, but it happens a lot. And I can imagine that the level of stress that these families experienced would make it worse, because small conflicts carry more emotional weight when you are already feeling defensive.