How does age difference affect inheritance among heirs?

Our Grandfather expired in 1986 leaving behind our grandmother, 5 sons and 4 daughters. He had one house. House property was purchased in the name of elder son’s wife, second son and our grandmother only for income tax purpose in 1977 and there is a criminal case still pending in the court because our income tax advocate fraudulently took the cheques in the name of other three sons and the amount was invested to construct the building. All the money was our grandfather’s. One son expired in 1997 leaving behind one wife and daughter. Now our grandmother, all the sons’ families, one divorced daughter , widow and daughter of deceased son are living in the building. How will this property be distributed in all the heirs? Are the persons’ in whose name the plot is(only for income tax purpose), considered as actual owners or custodians(amanatdars) ? Does the age difference between the children of our grandfather have any bearing on the inheritance(difference 20 years)?