Regarding property division between sons and daughters

Hi, This issue is related to my sister. My brother-in-law has 3 brothers and 2 sisters. And my brother-in-law's father passed away 5 years ago. Since then the other 3 brothers have almost isolated my brother-in-law and have been creating their own assets and not involving my brother-in-law in any case. They have huge building and other business started by the father, but no share is given to my brother-in-law and is forced to stay in a small apartment in that building without any share in the rents they earn. So my question is, can he claim his share in the assets created by them using the profits earned from the businesses started by their father. There is no will that was created by my brother-in-law's father. My brother-in-law just run a part of the business which is also almost under their control. The legal heirs are Mother, 4 brothers and 2 sister(One sister passed away).Need your sincere suggestion regarding this issue regarding my brother-in-law's equal right in all the existing property.