property documentation in a GP property

Good Day! Kindly advise us with the below legal issue, We have bought a property in 1984 via GP and in 2005 we consulted the GP holder to make a sale deed and hence they sent a person who is said to be mother paper holder and we got registered and till now there was no problem. In recent time we have legal problem stating the person who did the sale deed was died way back in 1960. And from there family they are saying property belongs to them. Everything Katha, Tax paid and position from 30 years we are there, what shall we need to do win this legal battle. Appreciate your Advice,