Maternal property

My mother's father(who is 95 years old) had 1 son & 3 daughters. My mother is the 2nd daughter among the 4 children. Before 5 years, my mother's sister-in-law requested my grandfather to wrote a WILL on her son's name. She also promised/convinced her in-laws (my grandparents) orally that she will provide some share(like 1 lakh each) to the daughters. Just few days back all 3 daughters was informed about this through their mother(who is above 85 years old). Nobody has ever seen that WILL copy yet. And we are not sure whether they have mentioned about this 1 lakh share in the documents or not. Now they are arguing - when their son(to whom the WILL was written) starts earning, that time they will provide 1 lakh each to the daughters. Please let me know, whether all 3 daughters are having the right to get the correct share from that house/property. Because comparing with the locality of the house situated, we guess the daughters share should be more than 1 lakh. Both of my grandparents are alive now. How to claim this ? please advice.