With a use and occupancy agreement and an intention of purchasing the home can we stay in the home until we purchase from the estate?

We’ve been caring for my grandfather and signed a use and occupancy agreement prior to his death. Now that he has passed we have an intention to purchase the house. He gave us 18 months to do this and no landlord tenant requirement after he dies. The two brothers are trying to kick us out however our grandfather’s wishes were that we remain and purchase the house from the estate at fair market value. We have this in writing. It is not in the will accept a clause about formal probate to protect interested parties at the time of his death.