Normal
You said your piece based on what you know from here and other kids like difficult child-nephew and got it off your chest. I hoover at family dynamics, but I think it's good that you said it. If you continue to tell him beyond this one conversation, I think that would put a strain on relationships, but I'd stop listening to him complain about difficult child-nephew until he's ready to do something about it and is looking for affirmation in the form of advice (i.e. when he asks for help with difficult child-nephew).