SSI

I would like to know what can be done about this situation. My aunt adopted her nephew in '05 in '06 she died and since she was already receiving ssi he also starting receiving it as well. but after she died he began receiving more. The hard part is that she (aunt) never appointed an guardian over him so he is basically as I was told a ward of the state. but his biological mother has him now and for the past three years she has been receiving his check even though she has been to prison. She is not saving anything for him she uses his check for her crack habit, her probation fee, I believe she is also paying her oldest son child support payment with it. She also has two other boys in the house which she is not receiving any money for. So she is basically living off his check because she do not work. My question is what can be done to stop this so that when he do turn 18 he will have some kind of saving. He is now 10. It is so sad the way she (bio mother) misspending his check.