My 4 year old nephew treats mom horribly?

Why is this in toddler/pre schooler question? 4 is not a baby nor a toddler.

Well... even if you figure out a good suggestion for them, how are you going to present this to them? Surely they’ll take offense and it will strain your relationship. I’d stay out of it. As for what caused it, I can only assume, but I’d bet he learned it from someone doing the same thing to him or to the mother, so, possibly the father or someone else in her life, or possibly he learned it in daycare from other kids, or possibly the mother says these abusive things to him. Abuse like This is learned, it’s not the typical hitting all kids go through and have to be disciplined for, these are abusive words he learned.

Your nephew could have neurological condition. His parents should seek help with a child expert . Doctor or similar incase the behaviour has underlying causes.

hope it all gets sorted out.

Because his parents allow it. YOU don't do anything. He's their kid.

Does he get any kind of discipline? if I'd called my Mom fat or ugly I wouldn't have been able to sit down for a week.. Does his Dad abuse his Mom in anyway? Kids pick up on these things very quickly, "if Daddy is calling her a fat b**tch then so can I."

He could however have an allergy, ADHD or even autism (of which there a five different types.) All these things need to be ruled out before he gets into serious trouble.

His mom probably doesn't have clear rules and boundaries. You can give his mum a few parenting books to read. Tell her to make some household rules and a consequence if they are broken. The consequence should never be physical discipline. Also tell her to treat her children how she would like them to treat her and be a good role model.

How are we supposed to know?

Spare the rod and spoil the child.

The kids 4 and u should probably take away things that he values when u misbehaves and when he’s good just give it back

No discipline. He needs his butt heated every time he acts out or he will get worse and worse until the day he sinks a knife in his mom because she didn't buy him something.