Would you say something

I basically raised my nephew when my sister lost custody of him. She was a very abusive mother so I had him most of his life. Me and him are really close and I'm the first person he came out too. Me, my son, my nephew, and his boyfriend, were all gonna go to pride parade today but his boyfriend has a habit of getting really mad and destructive. He got mad at my nephew and threw everything out their fridge and left it for my nephew to clean up so we ended up not going to pride. They were arguing upstairs and boyfriend came down stairs and smashed the TV off the mantle and left the house. It's the 3rd TV he's broken. There apartment also has 3 holes in the walls and they were evicted from their last apartment from all the damage he did to it when he got angry. I feel like this isn't my business. It's not my relationship. He's grown. But at the same time if I was with someone like this I would want someone to tell me I deserve better.