I don't know what state this property is located at, but you should know your state laws regarding your rights and theirs. Clearly your grandfather was taken advantage and they knew it. Waiting 3 years to try and attempt to reclaim the property also didn't help this situation. I don't know your grandfathers age or mental status but depending on the state you are in you should contact elder abuse because he was taken advantage of and robbed of his home. A lot of lawyers will do Pro Bono work (For Free). Try contacting a lawyer that will speak to you on the phone or give you an appointment free to discuss this situation. This lawyer may be able to advise you on what to do now. Also, a sharp property manager may be able to help you if you want to rent this place out. Last scenario if you are unable to get anywhere put the property up for sale. Let the Realtor know you need his help to remove them. Best of Luck to you.