Ancestral rights

I appreciate your expert views on the below mentioned topic: I had bought a residential plot of 40x60 ft from a non-NA land property in Bangalore in 2010. The property is under b-katha of BBMP & all taxes paid as on date. We are the 5th subsequent owners of the plot. The background of the land: The original piece of few acre land was owned by “person A” in 1979 and the “person A” had 4 children. In 1992 post the death of “person A”, all his children divided legally the property equally. One of the children “person B” (FIRST OWNER) in 1992-93 had sold his part of the property to “person C” (SECOND OWNER) and the sale dead is even signed as witness by son of “person B” and further the sale dead mentions that post the sale, neither “person B” or his legal heirs shall claim no right on the property & in case of disputes “person B” shall set right the issue, if any. “Person C” converted the land into 10 plots and sold them. In 95-95 one of above plots was sold by “person C” to person “person D” (THIRD OWNER). In 2003-4 “person D” sold the property to “person E” (FOURTH OWNER) and finally “person E” sold the property my wife “person F” (FIFTH OWNER) in 2010 and since then we own the property. The issue: Now one of the legal heirs of “person B” has put case on his father (person B) claiming he was minor in 1992-93 that the property belongs to them. I feel helpless though I believe strongly in our legal system, so please help us in knowing my legal rights. Like me there are 9 other persons who are getting impacted by this case.