Living in rented trust property from past 25+ years

We are living in a rented trust property from past 25+ years. All the trustees are dead now. We paid deposit while renting the house and used to pay rent monthly. After the trustee died no one has come to ask for rent from approx 8-10 years. Few years back a friend of one of the trustees (who was a lawyer) sent us a notice to vacate the house without showing any proof of his right on the property. So, we did not vacate the house and he never bothered us except one another notice he sent. 1. I want to know if we have right on this property since we are living here from so many years. 2. Is there any way we can sell the house? 3. If we leave the house and lock it then I am worried someone may take the possession from us. Is there any way we can keep the possession secured without living in the house.