Setlement Deed issue

My name is Rajan, My great grandfather had 04 sons and 02 daughters and he was having ransom wealth which he had registered a settlement deed into his 04 sons name on 15th May 1965 without any condition and he had clearly mentioned in the settlement deed that his ownership on the properties will be ended rights after the moment of his signature in the settlement. After 03 months, He found some issue between his sons and he went to the registrar's office on 24th Aug 1965 without any one knowledge and canceled the settlement deed, further he has registered a will deed authorizing his 04 sons and 02 daughters to inherit the property after his death and none was aware of the will deed until 1996. Meanwhile, My great grandfather died in 1967 and his 04 sons had divided the properties and registered (Patta's) in their name by using the settlement deed and all the properties have been under custody of the 04 sons offspring's in the last 5 decades. At the same time, my great grandfather's 02 daughters had not claimed any properties through legal way and died some years before and now one of the heirs of my great grandfather's daughter has filed a case against the 04 sons and demanded his grandmother shares from the properties according to the will document even though pattas are not registered in his name in the last 50 years. Therefore would you please answer my the following queries : a)  which deed has more valid settlement deed or will deed " ? b)  did the revoke of settlement deed valid ? c)  Can the heirs of 02 daughters of my great grandfather win the case in the court ? Please advise me. Thank you