Nephew Lives With Us But His Mother Collects His Survivor Benefits

I was told to post this here as I may get better advice than in social security sub.

Our 14 y/o nephew has been living with us for the past year. He was getting into trouble at home, with the law and in school until he started living with us. There is no formal custody arrangement. He just moved his stuff in our house and his mother gave the ok for him to attend school in our district and signed the necessary paperwork. Since he moved in she hasn't helped with anything for him. No lunch money, field trips, extra food, nothing. He has been receiving survivor benefits since his dad passed away when he was 6. My question is, can we do anything to ensure his benefits go to him? We will continue to support him anyway possible regardless if the support comes or not, it would just be easier with the support.

Additional information not in the original post: We live in Michigan, as does the mother (she's 20 minutes away)

He visits home maybe once a month and is usually the one that has to reach out to see if it's ok for him to be there.

The mother will not give me emergency medical care permission, we must call her and jump through hoops to get him medical care and treatment. We have had to take him to the hospital, but they refused treatment until they spoke with the mother.

When my nephew was 13 she kicked him out of the home multiple times because of his behavior. He came to stay with us each time.