Right of Children on the mother property where existing house was rebuilt by father

My father-in-law has 2 brothers and one married sister (married in nepal). The house was inherited by my father-in-law's mother but later on it was demolished and fresh construction was done by my father-in-law's father. Father in-law's father is not alive now. The mother of my father-in-law now is trying to do unequal distribution among four children (3 son and 1 married daughter). The ground floor and first floor is constructed. She is giving first floor to youngest son and daughter and is asking 2 elder son to build above first floor. The shops on the ground floor also she is diving in unequal manner. Since, the income of my father-in-law's father is put during the construction on the land (I don't know if they have the proof of amount invested). whether my-father-in law can do anything about it as there is un-equal distribution of property? Also his mother is mentioning that if all are not accepting this distribution then she will write it to one person. Can she do this? I think they are paying the tax of this property from the earnings of the property acquired by 3 sons from his father, which was fair distribution of property?