I agree with Attorney David. Depending on what you find out, it may be necessary to have two probate estates open, if the title was never transfered to your mother. You might find, however, that title was made joint with you, in which case, probate may not be necessary. I would contact a probate attorney to help you investigate this and determine where you stand.
*** LEGAL DISCLAIMER I am licensed to practice law in the State of Michigan and have offices in Wayne and Ingham Counties. My practice is focused in the areas of estate planning and probate administration. I am ethically required to state that the above answer does not create an attorney/client relationship. These responses should be considered general legal education and are intended to provide general information about the question asked. Frequently, the question does not include important facts that, if known, could significantly change the answer. Information provided on this site should not be used as a substitute for competent legal advice from a licensed attorney that practices in your state. The law changes frequently and varies from state to state. If I refer to your state's laws, you should not rely on what I say; I just did a quick Internet search and found something that looked relevant that I hoped you would find helpful. You should verify and confirm any information provided with an attorney licensed in your state.
There are not enough facts to provide you with detailed direction. You should contact a local probate attorney to review whatever information you have. You'll need to determine the title to grandfather's property; was it properly transferred to mother? Does that estate require administration? Once the grandfather issue is resolved, you'll have to do the same thing for mother.
When responding to questions posted on Avvo, I provide a general purpose response based on California law as I am licensed in California. In reviewing my response, you are specifically advised that your use of, or reliance upon any response I provide is not advisable. I do not have all relevant background details or facts related to your issue / matter, thus I am not in a position to give you legal advice. Further, your review, use of, or reliance upon my response does not establish an attorney-client relationship between us nor does it qualify as a legal consultation for any purpose. For specific advice regarding your particular circumstances, you should consult and retain local counsel.