DNephew is 8. We suspect he's ND although assessment process and referral only just starting. He has also had a tough time at home with an emotionally abusive and controlling, borderline-violent father who is now largely absent from his life. I mention thi sbecause I do acknowlege that he's had a bit of a tough start in life.
However, his behaviour can often be appalling. This has been true since he was a toddler. From our perspective (me and DH), his parents are/were ineffective with no consequences but lots of shouting. Totally pointless. The result is very normal for other adults to step in and discipline him. We (me, DH, other extended family) have all agreed to do this as little as possible and have really stepped back because we don't think appropriate, even though SIL actually likes it.
There was an incident at the weekend where a third party adult gave him a very serious ticking off as DN was speaking very very rudely (swearing and shouting and using very derogatory language) and SIL did nothing. I wasn't there so I don't know the details, but there's been some tension as a result.
Speaking to SIL is pointless - DH and MIL have tried fairly robustly. I've tried gently. So most of us just avoid doing things where he will be forced to be around us as he can't/won't behave and his mother refuses to deal with it.
But he's getting older. Expectations are higher. And I'm worried. He's on the verge of being kicked out of his sports team for poor behaviour and it appears he no longer has any friends at school. I suspect there are more consequences that I'm unaware of.
Would it be insanely rude to say to SIL, next time this sort of thing happens, "Are you going to just let him speak like that to you/me/DH/random person on the street?" It feels so passive aggressive but something has to change!
Oh, and before anyone asks, for the last year DH and I have really tried to engage with him positively, speak to him about good things going on, include him in events and outings etc. But mostly he refuses to participate and stays home on his xbox and SIL doesn't seem able or willing to push it.