enquiry about an unregistered WILL

sir my gradfather left an unregistered WILL in 1965.in that he states that out of his 5 sons ,three sons have male issues .the remaining two have no male issues as on 1965.ONLY SONS WHO GAVE MALE ISSUES CAN ENJOY HIS PROPERTY.But in 1969 the last son of the 5 sons have a male issue .that is me.iam born during the life time of my grandfather .he dies in the year 1972 ,three years after I was born .MY QUESTION IS AM I ELIGIBLE TO INHERIT LEGAL AND RIGHTFUL SHARE OF MY GRANDFATHERS PROPERTY...PLEASE ANSWER MY QUERY?