State law covers this situation. Talk with a local probate attorney who can tell you about how his property should pass to his heirs. Then if the mother is the heir (assuming the law disallows the wife from inheriting) I believe the refund claim form 1310 states something about that the person requesting the refund will pay it out according to the laws of the state.
I would not request that refund until you know who is actually due that money. Probably the mother but you never know.