Unregistered family partition what to do

My grand father property is divided by three sons A B C , C is my father revenue land they have registered in 1992 . But site and house not registered . In Rs 100 stamp paper and in plain white paper both same matter they have made partition and taken signature and thumb impression of ABC .1998 in plain paper and 2006 Rs 100 stampaper . A Has one house and B has one house and 3 sites and C has one house one site . Here A has little less property because he has taken more revenue land And now also changed the documents from my grand father to C in grama panchayit recently . But A is trying to cheat us .is it possible to him . What precaution we can take .now they are telling its not registered .