Nephews mother collects his survivor benefits but he lives with us.

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. Even when asked to help with these things we are told "we'll see" which always results in being ignored or accidentally being told they "can't afford the extra right now". Meanwhile her and her new husband spoil the child they have together (nephews half brother)

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. I really don't know what our options are considering a judge would have no reason to award us custody.