Need advice on Property Issue

Hi, I am asking this Query on behalf of my "Brother in Law". Story begins with his Late. Grand Father. - He had three son. - Had many properties in the name of himself and his wife - He had arrange for housing for family of his three son. - He also had few shops which He had distributed to three son - He did not divided properties on paper but only allocated housing for three member as per understanding in family and all three family was living on their allocated house separately. What is dispute? - Dispute is on a House which is located in Premium location and it's priced more than 5 Crore now. - Family of two out of three son was living in this House, Two separate floor ( Ground and 1st) - Family of third son was living in their allocated house whose price has not increased same as this house. - Now member of third son family demanding selling of all property of Grandfather so that they can also get share in the House whose price has increase exponentially. Some other facts: 1. Father of my Brother in law is also expired. 2. 3rd Son (Eldest one) is also expired 3. Only one son of Grandfather is alive and who is also staying on 1st floor of Premium Priced house. 4. Family member of 3rd son demand selling of this premium house and 2nd son also agree with their demand and want house to be sold What my Brother in law is saying? - Since Houses was allocated by Grandfather's time and his three son's famly accepted that at that time, So now this premium house belong to them alone ( along with 2nd family). - We do not want to sell it and no one can force us because this house was allocated to our father by grandfather while allocating housing for all three son. The paper of House which is in the name of Grand Mother is also in possession of my Brother in Law. Please advice what is future of this dispute and what are the legal rights of my Brother in law and his family. Thanks & Regards, Kheteswar