From the context of your post, I assume that your grandfather has died and that your father holds title to the property and has taken out a reverse mortgage. If this is the case, then upon your father's death, or if he moves out of the property, the reverse mortgage becomes due. If the loan is not then paid off or refinanced, then the reverse mortgage lender can foreclose on the property.
With respect to your grandfather's trust, there's a distinct possibility that you were were only named as the contingent beneficiary who would inherit the home only if your father died before your grandfather. Ask your father for a copy of the trust, and review it with a trusts and estates attorney.
From the context of your post, I assume that your grandfather has died and that your father holds title to the property and has taken out a reverse mortgage. If this is the case, then upon your father's death, or if he moves out of the property, the reverse mortgage becomes due. If the loan is not then paid off or refinanced, then the reverse mortgage lender can foreclose on the property.
With respect to your grandfather's trust, there's a distinct possibility that you were were only named as the contingent beneficiary who would inherit the home only if your father died before your grandfather. Ask your father for a copy of the trust, and review it with a trusts and estates attorney.