I have property civil suit pending. Please suggest me

In a civil suit, the petitioner filed suit for declaring registered gift deed executed by her as null and void. The gift deed was executed in 2002. The petitioner filed the suit in 2013.In the suit, she says it came to her knowledge in 2006 that said gift deed was fraudulently done.She says being Senior citizen she could not file suit for 7 years from 2006 to 2013. It is clearly time barred as per article 59 of limitation act. The plaintiff expired in 2014.Two of her sons have become plaintiff LR1 AND LR2. To avoid limitation act, they have sought amendment saying they have come to know about said gift deed only in 2013. Question is can LRs change the original petition of plaintiff by seeking such amendments. If allowed so the defendant shall lose benefit of time lapse as rule 59 of limitation act. Should such an amendment be allowed although trial has not started.