Since mineral rights are considered real property his estate will have to be probated in each state. This will be costly, if this were in Wyoming it would cost a minimum of $2500 up to 4% of the appraiesed value of property in each state. Court costs, advertising, appraisals and legal fees. I suspect it would be the same or more in each state. It can usually be done by deed, trust, LLC or corporation. You need to contact a lawyer familiar with mineral estates in each state to transfer his interest in the minerals to his heirs as soon as possible. It will cost much less to avoid probate. If you don’t know any attorneys in each state, go to each state bar directory and look for attorneys in the county where your minerals are located. Or call the county clerk in the county where your minerals are and ask them for a list of attorneys that handle mineral rights.