S.B.
Listen....
that child has problems.
And, in my opinion, for one thing, your 78 year old mother is in no condition to try to raise a child who needs this much help. A 78 year old trying to raise an ANGELIC 6 year old is too much. Where your sister's head is, I have no clue. (No offense).
I'm surprised with the child's history that someone hasn't stepped in to take a closer look at what's going on at home because seriously, your nephew could be headed for serious, serious trouble.
My nephew is 4 years older than my son and he went through a phase of being mean to him and thinking it was funny. For no reason at all, he would just haul off and punch my son in the arm or in the stomach. HARD. Knocked the wind out of him. Left welts on him.
The difference in my case is that my nephew got in BIG trouble! His parents, my mom, me....we didn't pussyfoot around about it.
I wouldn't let him come stay with me no matter how much he begged because he wasn't nice. I wouldn't let my son alone with him at their house because he wasn't nice.
Avert your eyes for those who are sensitive, but there were a few times my brother in law just out of the blue slugged my nephew in the arm. My nephew would be like, "Why did you do that to me?" And he'd say, "Why did you do it to your cousin 10 minutes ago? It's not that funny having someone bigger than you just punch you, is it?"
My nephew got the gist. And, I'm certainly not advocating that in your instance. My nephew didn't have all the issues your nephew has.
Until or unless they get a grip on that child, I wouldn't let my son out of your sight, or around that child, and your mom and sister can just deal with it.
The child has agression issues that even have presented with sexually assaulting children.
If they can't see there's something wrong with that, I don't know what to tell you other than to keep your child safe from harm. You can't fix the other child. And if child protective services hasn't stepped in by now, perhaps they never will, but he's on a path of destruction and I feel sorry for him.
I don't feel sorry for him to the extent I'd let him have a chance to hurt my child, but he doesn't seem to be getting the help he needs.
It's a bad situation.
I wish you the very best. I really do.