Distribution of land among hairs?

My father in law's own father have 150 bigha of land which he divided have among his six son equally i.e 25 bigha each. The distribution of land is mutually & there is no documents apart from the original registration paper which is registered on my father is laws own fathers name i.e my father in law does not have any documents on his name. But now my father in law want to sell his part of land i.e 25 bigha. But all his brother is asking for 1 bigha land from my father in law & if he does not give 1 give land to each of his brother i.e total 5 bigha land out of 25 bigha they will not allow to sale his portion of land. What he should do now to sale his property. and how much money and time it will take to solve this problem