I have been paying child support for years on my son who is deceased. For years,part of my support was sent to his maternal grandmother,who was in prison at the time. Even though,during this time,I had custody.I was on ssi before the court ordered that I had to pay.What should I do?

You were paying support for someone who is deceased? You had custody of someone who is deceased?

Please clarify the contradictions in your question.

SSI is not exempt from support. If your situation changed and you did not file for a modification, then it may be too late to correct it for the past.