Uncle not ready to divide property as per grandfather's will

Dear Sir, My grandfather has written a will in Jan. 1988. He died in mid of 1988.Which I dont know registered / Unregistered/ But it is Notarized and Attested by Lawyer. My query is : - My late grand father is having a wife and 3 Sons and He distributed agricultural land in the name OKC HUF RKC HUF JKC HUF DURGA DEVI 1/4 Share to each (3 sons HUF and Wife) But post his death Majority of agriculture land has been named under my uncle. This agricultre land reflects under my Uncle OPC`s name on (JAMABANDI - NAKAL) Query : - Since In will all agricultural land was divided amongst equally 3 sons and wife. But post death it has been named to My elder Uncle`s Name. Can We challenge it and ask for equal share in the property? Since uncle is denying for the transfer of property. Please advice what we should do? Since the property on Tahseel Daar records reflects under elder uncle`s Name.