Deceased Owner's Nominees

Before I start my case I would like to give a background to make it easier to explain. This is a property ( house) related case which is in the name of my deceased grandmother. My grandmother (widow) had two sons and two daughters. All were married at the time of purchasing the house. The house was purchased by my father and grandmother in the ratio 2:3 (respectively). However the property was registered under the name of my grandmother and nominees were her two sons. The younger one was already settled in Mumbai and was just a occasionally visiter. While my father( the elder son) has been living in the house. She later died (after 4-5 years ). Since then her elder son's family has been living in the house and has borne all the expenses regarding repair/ Coloring , water,etc. However now that we are willing to sell out the property the two sisters are creating problem as they want some share too. I find objection here as first of all the house was bought by my father and grandmother. Still the nominees included my uncle who never lived in this house and never even contributed 1% of the house repairing expenses in the past 17 years ( since the house was bought) . We could have just lived in a surviving environment but we repaired the house , coloured it, equipped it with facilities which has appreciated the value of house a lot. All by my father's money. I don't understand how my uncle is going to get even 50% just because he is a nominee. My father's share should be more. And moreover now his two sisters want it too whereas they aren't even nominees. Can we win against them . I'm kinda confused so I'm seeking prior online help as I'm unaware of the various law related to nominees and legal heir. And what is the speciality and exception regarding this case. I will be waiting for your response.