Protect Paternal Agricultural Land Against Malevolent Move From Non-family

Hello Sir/Ma'am, Some people (non-family scheduled caste) are trying to influence my grandfather to write our paternal agricultural land in their name. Since my grandfather is more than 90 years old and doesn\'t remember things very well, I fear that they may convince him to sign it in their name or produce a fake claim of some big amount against our land later. I also worry under any dispute with us in future they may not additionally register case under SC/ST act. Kindly advice how I can cover my family assets against any such prospective malevolent move from their end in the future.