How can i make sure that my gift deed is not challenged in court

my grand father gifted part of his property to me by registered gift deed. two years ago, which i done mutation in mcd office also. my grand father has 3 sons, 2 daughter. in his old age i m looking after him of all his needs. so he gifted me some part of property, rest of property has a registered will also, in will same part of property is on my name also, but to make more lawful, my grand father gifted to me that part. As he is still alive, he wants to know, can any of his sons & daughter can challenge that gift deed. He doesnt want anyone challenging my right on the property, after his death. Is there any more document which can be saved? This property is freehold, self earned property of my grand father...as mentioned by many lawyers that registered gift deed can be challenged, then what is the best way to safeguard my interests? gift deed registered gift deed How to avoid challenge to gift deed