Step mother children laws.

Hi Sir, My grandfather had married my grandma and had 5 children. Among them my mom was the eldest. After my mom got married my grandmother died. My grandpa married another lady. The lady has 2 sons. Down the lane my grandpa informed my Dad to buy and sell his current property due to debts. But the property was not under my Grandpa's name, it was under a different landlord name, who sold it under my Mom's name and my Dad sold the land, with the money covered my grandpa's debts 30years back. My Dad to passed away 17 years ago. Now recently the son's of the step wife called my Mom and asking for money and property as they are not well now. If she's not giving anything they are mentioning as they will file a case against my Mom. But my Mom do not have any property currently under her name. And she's a retired Govt. Senior citizen getting pension. Those step wife son's are torturing my Mom calling and saying we will file a case against you and giving mental tension to my Mom. Please let me know a solution on this. Thank you.