If he died with no Will, each State will have laws specifying how the assets are to be divided/awarded.  Usually it will first go to a spouse or 1/2 to spouse and other 1/2 to deceased's children if they are not also spouse's children; then children, then to parents, then to siblings, etc.  Son may or may not need to initiate a probate proceeding to settle the matter.  Son should see a local probate attorney to at least learn his options and anticipated costs.