What to do if I feel like my nephew is being neglected?

He’s not being abused and he’s being fed but I feel he’s being emotionally neglected.. unfortunately he’s the only kid and he doesn’t have any cousins. I asked him if he had any friends at school and he didn’t respond. I also found out he doesn’t have any play dates as well.. he’s only 7. Unfortunately my sister has inherited the “anger snap” from my mom where she’ll just snap in anger and then go back to normal… I saw her do that a few times with my nephew tonight.. I’m kinda worried for him. He’s a good kid yet he gets yelled at a lot by his parents.
What to do if I feel like my nephew is being neglected?
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