Legal Question in Wills and Trusts in Oklahoma

Was she awarded the house in a divorce proceedings? If so, no, her ex-husband is not entitled to the house.

You need to find out who holds the mortgage. Talk to them about what they wish to do. The decree should address who is responsible for the mortgage. If your grandmother was responsible and died before the mortgage was paid off, then the bank or loan company will foreclose on the house to pay off the mortgage. The bank should have filed a creditor's claim in this probate. If a creditor's claim has been filed, your probate attorney needs to decide what to do.

Your grandmother's ex-husband is not entitled to the mortgage based on the facts presented.