Claim on great grand father's property (agricultural land)

My grandfather has inherated agricultural land from his grandfather's. He (my grandfather) has five children- two sons and three daughter and is now 97 years old. He has now decided to share a major portion of the property, agricultural land and house between his two sons and a minor portion between the three daughters. They argue that my mother, (who is now a widow) was born before 1956 (she was born in 1954) and was married in 1970 and has no right on the property. One of my aunty is claiming that the property be divided equally among the five children (she was born in 1960) else she will take a legal recourse. My uncles argue that the property was divided by my grandfather years ago and the Katha was issued in their names and are reluctant to divide the property equally. Can you please suggest if the women of the house can claim equal proerty under law (Hindu Succession Act, 1956), . In other words, can my mother and her sister claim rights on their great grand father's property. Can they challenge the Katha issued in my uncle's name