Land sold by Co-owner

I purchased a piece of agricultural land in Odisha almost 17 years back and now there is a dispute as below. The land belonged to 3 co-owners (A, B, C). They are our neighbors. Each person had an equal share in the land (1/3rd share). Long back "A" sold his share of the land to some other person (D). Similarly, 17 years back "B" sold me his 1/3rd share of land. Since then I am doing cultivation in that land. 1 year back I got the mutation done for the land which I purchased from "B". The share of "C" is still as it is, and he has not sold to anyone. But now, "C" has issued a civil suit on me stating that during the sale of the share of "B", his consent was not taken. Yes it is true that when B sold his share of land, the consent of C was not taken. But A and B each of them sold their own share leaving 1/3rd share of C. My query: 1) Is it mandatory to take consent of C when B sold me his share of land? 2) Considering the fact that for last 17 years I have been doing cultivation on that land and now I also have the mutation done, how can I defend my case?