Property claim after 30 years

Hello Mr. X got property from his father thru compromise decree in 1979 and he then sold it to Mr. Y in 1980 and we purchased that property from Mr. Y in 1982 with GPA Registered and in 1982 got sale deed done from Mr. Y and in 1984 we paid betterment charges to govt and got A Khata and till 2018 we are paying BBMP tax and all EC records are in our name. Now Mr. X father other grand children are claiming our property as there grand father property and showing revenue land records are still showing there grand father name. But the property was converted to BBMP in 1982 itself and 5 acres 15 guntas was converted to sites in those years and sold to different parties. These grand children who ever construct in the sites in 5 acres 15 guntas land they will send lawyer notice claiming for there property or otherwise pay money thru compromise so that they will not disturb thru legally. Kindly advise how to go about it in this regard. We have Mother deed registered, sales deed, A Khata, Tax paid receipt, EC in our name, Power and water connection till date