Gpa registration in bangalore

Hi All,

I need help and possible solution on the issue that we are facing on revenue site that we purchased in year 2005 in Bangalore.

Issue:

History

1) As per land record sole owner (Person A) of the land, sold this land through GPA to Person B in the year of 1980. However during GPA transaction its clearly not mentioned how land is sold to Person B. (only survey number is mentioned)

2) Person B, sold this land to Person C through proper registration process, however during registration Person B didnot take any signature or Approval from Person A.

3) Person C sold this land by dividing into individual sites (he didnt allot any site also land is not converted from revenue) 

4) Since revenue land registration was allowed till 2005 year in Karnataka we purchased site from Person C.

Now Grandsons, wife and sisters of Person A (sole owner) claiming GPA registration is illigeal and they have cancelled GPA and asking us to register property from them. (By paying 50% of property value).

So I need some suggestion from members/Lawyers on this matter, Please help

Is it required to go for fresh registration? How to get Katha transferred to my name just incase if government allows converting revenue land by paying development charges?

Thanks

Natraj