Recently my boyfriend and I signed papers a Custodial Affidavit so that his nephew could live with us and attend school in our town. The mother had a Parent Affidavit. None of this had to go through the court system, just the school. Since then my boyfriend and I have are separating, since this is his blood relative I am going to relinquish my custodial rights here. How exactly do I this. Again, none of this was done through the court system, only through the school which is how the school told us to do it.

I don't think you have to do anything. I suspect the school had you sign something just to cover them. But it really had no legal force. I don't think you can be held responsible for the child. If anyone tries tell them to take you to court.