Can my husband receive retroactive disability benefits?

My husband was deemed disabled from the age of one and his mother was receiving disability benefits for him. He is now well of age and can receive them on his own. He hasn't received any money since 1998 due to the fact of his disability and not being able to function on his own. His mother was receiving money on his behalf illegally up until about 4 years ago. Money he should have been receiving. What should he do?Can my husband receive retroactive disability benefits?
He can pursue this in court and most likely would be awarded a judgement. The downside is that this is his mother and unless she has significant income or liquid assets, the judgement won't mean much of anything.