how can i take my property from the previous owner?

I finalized arnd 6acres land near vellore dist, tamilnadu, from a land owner which he received recently (Feb2015), by his family partition(ancestral property). He has 3 sons. He wanted to sell his land. my self and him executed an sale of agreement and registered the same saying, the seller received advance, n will make sale deed within 3 months from the date of agreement. Now almost 80 days gone, he is not responding, not attending my call.. Shall I move to court. With the agreement of sale registered between myself and him (without his sons) shall I pay remaining amount in court n get it