You want to get them away from that situation but directly asking if their father is abusing them can backfire if it isn't done at exactly the right time.

I haven't seen any immediately visible injury marks on their hands or wrists or necks, but I was anxious about that and expressed my concerns with his wife. The fact that he sometimes raised his hand in anger in a "want to hit them" motion but didn't because "he just felt that way" even without landing the blow when they did something as rage inducing as... not getting their seat belts on fast enough... made me feel a little sick inside too.