You can determine the answer to your question by reviewing the mortgage note and the property grant deed. These are two separate documents that hold different legal meaning.
The mortgage note outlines who is responsible for repaying the mortgage on the property. Simply put, a person is either a borrower on a mortgage or not -- there is no in between or different distinction -- and the mortgage note shows all parties that are legally responsible for the mortgage. If there is more than one person legally responsible for the mortgage, also known as co-mortgagors, then all co-mortgagors are listed on the mortgage note.
The grant deed is separate document that indicates legal ownership interest in a property and how that ownership interest is held. For example if one person owns a property he or she would be the only person listed on the grant deed and that person would own an undivided 100% interest in the property. If a married couple owns a property together then they would both be listed on the grant deed and typically hold title as joint tenants or each person would own an undivided one half interest in the property (if the ownership is equal). If more than two people own a property each individual as well as their ownership interest would be listed on the grant deed. It is possible that title / ownership interest in the property might have been changed or transferred after the initial recording of the grant deed. Any change in property ownership must be recorded so check with your county recorder's office to determine the current ownership of the property.
Please note that the mortgage note and grant deed are two separate documents and it is possible to hold an ownership interest in a property without being on the mortgage note (and being legally responsible for the mortgage). I recommend that you review the mortgage note and grant deed for your property and contact a real estate attorney if you have any questions.