If the kids are in YOUR home and behave badly --- tell them to stop whatever it is they're doing. You're entitled to expect good behaviour rom then wen they are in your house. If they are misbehaving in their own home, and their mother is too stupid or herself too bad-mannered to have taught them how to behave properly, your best bet is just not to visit them there. Arguing with your friend won't be useful, as you say. But there's probably no harm in chatting calmly to him about how you find the kids behaviour highly irritating, and asking how he feels about it. maybe they annoy him too, but he hesitates to comment because he doesn't want to annoy her