The best way to ascertain if your parents' mineral rights are in a trust is to first look at the trust as well as any recorded deed in the county and state where the mineral rights are located as to a given parcel to see if legal title has been placed in your parents' trust. If your mother goes on Medicaid, it may have a claim to the mineral rights for reimbursement of medical care. I suggest that you consult with an estate planning attorney in your locality as to your inquiry. One can be found on attorneypages.com.