Your mother needs to transfer the deed to whomever is going to assume it. You should be able to this as a Quit-Claim Deed. I would suggest that you contact a lawyer to prepare the deed. Then it is just a matter of taking to the Recorder's and Auditor's office to file it. Prices vary widely by county, so I would contact them to find out what you will need to make the filing. Alternatively, you could request the attorney you hire to file it for you, but you would be incurring some additional cost.
I'm confused by your question. Sounds like your father died and house is still either in his name or their joint names; and I have no idea what your mom's father has to do with this. In any event, you are going to need either an expert probate attorney or real estate attorney to help you. This will cost a few hundred dollars. There are very fine Cincinnati-area probate attorneys who participate on this forum and who would be able to help you.
Mom needs to take a copy of the existing deed to a probate attorney. The procedure you need is not expensive but gets more complicated the longer you wait. Use to find someone in your area.