Our NRI relatives asking us to vacate our house in 15 days what to do

Sir/Mam I'm a Hindu. Actually my father worked for a aged person who had an adopted son. That aged person was more attached to my father than that person .his son was a evil minded and during the last days of his father he transferred the property on his name later he flew to USA.. my father and our family took shelter in a small room of his house which he got as a bumper draw.its been more than 10 years he left to USA. His wife recently came to us and asking to vacate the house. We actually taking care of the house like maintainance and etc and also it was my father who took care of the old person in his bad and last days actually his service to that person was very caring..and his adopted son only wanted the property other than nothing My question is that can I claim any property ?? Or should I need to stay calm?