What is the validity for land registration if not yet done Kathe

Hi Sir, Here we have issue with rural land property. Actually 10 years back my father has took (2 lakhs only) money with my uncle, for that he has(uncle) taken land of 12 arcs from my father( my father has registered 12 arcs land). after that there is 6 arcs land left over there, again in 2009 he as forcefully fight with my family and took that remaining land also. in 2009 we have registered that land 6 arcs, at time he has just registered and whole my family members signed in that registration document except my sister, now problem is after registration of 6 years that property 6 arcs its kathe showing with my father name and still TAX is coming with my father name only and even past 5 years that tax has paid by my father, Now kathe comes with my father name and tax also paid by my father, so is it Valid that registration ( 6 years over), but here EC comes with my uncle name and Kathe and Tax come with my father shall we proceed for cancellation of registration and what is the validity for registration? or go to court for my sister was not signed at that time of registration. Kindly provide you values suggestion/answers. whole family is depend on this property. there is no other source for my family. Thanks in advance Regards, Siva