I have legal guardianship of my nephew. Permanent guardianship. The mother is always trying to get him back although she is not fit to have him. What does a judge consider before determining a guardianship is no longer needed?

What does a judge take into consideration before terminating my guardianship of my nephew?

We need more info. Like where does this take place, how did you get guardianship in the first place, how old is the child, how long have you been his guardian, etc.