What legal steps if uncle demands grandfather’s house eviction?

My family has been living in my grandfather's house, which is still in his name. He passed away without transferring ownership to my mother, even though he had intended to do so. Now, my uncle wants us to vacate the house, as he wants the property for himself. My mother is not involved in any probate proceedings, and we’re unsure how to respond to our uncle’s demands. What legal actions or steps should my mother consider in this situation?