jM: In short, the production from the minerals is called royalty. It is possible to convey one & not the other but under the information provided I doubt they were ever differentiated. If there are no conveyances then inheritance is per the laws of succession of the state where the minerals reside. There are different rules for those with Wills & those without. It sounds like you need to do several Probates to get the title into the proper parties. You should gather all the heirs information possible & hire a lawyer to get things in order.