false F.I.R. for property

My mother-in-law (widow) has two sons and two daughters. both daughters are married and living in their respective homes. Elder son is married & living separately. Younger son who died recently, was living with his wife and my moth in law and was married from 7.5 years and has no kids.The house they were living is registered in the name of my Mother in law. after his death his widow filed the false F.I.R. against my mother in law, both her daughters and elder son & his wife in sections 307 and 498 A. Police not investigating the case rather they are more interested in reaching some kind of agreement. In the name of agreement they are saying that divide all the property of the family in two equal share one for each son and give full share of deceased son to her widow.They are also including the properties which are already registered in the name of different family members. My mother in law has 3 houses in her name, they are saying that leave only one house for my mother in law and rest two houses are also to be divided between two sons.My question is they are not giving any share to mother instead they are taking the property which is already registered in her name. please advice what should we do to bring justice to my mother in law