I want little to do with my nephew and his mother
What is the matter with them?
I just want to reduce my contact with him until I can get free from them completely, but don't know how to do it exactly.
It's okay to want time away from your relatives. Sometimes people need to establish boundaries for themselves and your relatives should respect that.
The kid is horrible, I know for sure, and the mother is stupid for letting people babysit him. I'm going to say it in court and he will be to happy being with a better family.
If you go against your family in a court room you may end up doing irreparable damage not between you and just them, but possibly with other members of your family as well. Why not try working on them about any issues they have first and see if you can help them fix things without involving the law?