About will

My grand father has got 3 sons and no daughter. My grandfather expire on april 2015 at the age of 90 years due to last stage of lung cancer, after one year of his death we came to know about a will from his younger son means our uncle that my grandfather had made a will got it registered on july 2014 in favour of his younger son the third one providing his all the the sole owner for all bank accounts , PO accounts and a own earned house. Till now we were not having a single dispute in our family but after we came to know about this will all got upset, Both the elder brothers were not given any share as both are well settled and have own houses as mentioned in the WILL. Suprsingly nothing have been left in name of my grand mother aged 88 years not house or bank and post office accounts. But the fact is Post office accounts were in the name of My grand mother. We also have a doubt is signature mismatch as sign on will are differeent and sign on registered will area where all stamping are done are different. Please do provide needdfull assistance.