Property Ownership rights

Dear Experts, My grandfather from mother's side bought a property back in 1978 and as he was not that educated the lawyer named the property paper GPA under my grandmother's name but the signature was all done by my grandfather only. after few years my grandfather's son (my uncle) suggested my grand father to transfer half of the property to my grand mother's and for that a Notary attested GPA was done and hence half of the property was transferred to my Grand mother and the Electricity connection got registered under my grand mother's name. But back in October 2013 my grand mother expired. My Grand parents have 5 kids, 3 daughters and 2 sons. One of aunt got married in March 2015 and for her marriage my grand father had to take loan and after a discussion with lawyer he suggested that the property was under grand mother's name so it needs to transferred to grand father through an R-Deed so for that R-Deed 3 daughters signed but sons refused to sign and we Did that R-Deed for the 4/6 share of the Property under my grand father's name and left 2/6 portion for my uncles. But now they have filed a case against my grand father and against 3 daughters stating that the property was under grand mother's name and they are looking for their share. In Mediation when we agreed to give them the 1/6 from my Grand mother's share they said they are looking for 1/3 both sons. Please advise how can we solve it out and will it help too file case in Senior citizen cell.