I can't give you definite answers from the information you provided, but I can give you some suggestions of how to proceed. You are trying to sell your mother's home,
without her leaving a will.
The first concern is how she held ownership/title of the home. You state that there was another "joint owner" who has also passed away. Did your mother and the other owner hold title "in joint tenancy" or "as joint tenants?" If they did, the survivor of the two of them would have become the sole owner of the house. So if the house was held in joint tenancy, the crucial question is: who died first, your mother or the other owner? If the other owner died first, your mother would own all of the house. If your mother died first, the other owner wold own all the house.
If the house was not held in joint tenancy, then your mother's interest in that house would be part of her estate. I can't tell if you believe that your mother owned all of the house, or just part of it. What happened to the interest of the other owner?
Again assuming that your mother had at least some interest in the house when she died, that property would have to go through a court probate proceeding, to transfer it out of her name to her heirs (not "airs"). Because your mother did not leave a will, her property would have to go through a special type of probate proceeding, called an "intestate" proceeding. ["Intestate" is legalese for dying without a will.] To file an intestate proceeding you'll need to hire a probate lawyer.
In an intestate proceeding, the property of the person who died goes to the person or people defined as inheritors under the intestate law of the state where the deceased person lived. Generally, intestate inheritors are the closest legal/blood relations of the person who died. However, you must know exactly what your mother's state intestacy laws provides regarding inheritors.
In sum, in my opinion, you have some work to do, or to get done, before you'll be able to sell the house.