Old promissory notes have given during the renewal promissor

We have 3 brothers and given money for agricultural purpose to lease 50 acres for cotton cultivationin other state.Each one was given 3,00,000 money to one person on same day based on 2 years.after 2 years were over but he cann't paid single paisa.we called by phone regarding for the amount he replied this year cotton was not good.so that I want to sell 2 acres of my agriculture land for that I need 4 months time.until we wait for 4 months.but no response his side.so by phone no use, we went for personal approached. He told to ours , I came to my village and stay there for sell the land until I don't have money. In this process 6 months were over.one day he came to his village.my parents informed to ours.we went to his village and asked for the amount I stay here 1 week so if possible sell the land other wise I want renewal the promissory notes. After 2 days, we went along with 2 witness and asked renewal the pronotes.For that,he was accepted.he told to ours I want to pay that amount within 3 months.my aunt was lived in his village and near by to his house. Earlier,My younger brother took the amount from me and my elder brother so that his pronotes amount was completely wrote with our names. She wrote the 6 pronotes and earlier notes was also she wrote and 2 witness also same.at the time of pronotes execution we have given old pronotes to him. After 3 months over,but he cannot do anything wait for 2 months. No reply. We approached layer and send notice to him. But no response from his side.Then file the money suit in the court like this way: "The defendant herein became indebted to the plaintiff on account of financial transactions between them and in order to discharge the said indebtedness.he has executed 6 pronotes". He was contested in this case and written statement he mentioned like this way: "This defendant is an illiterate and an agriculturist.he has had never any financial transaction or dealings with the plaintiff.this defendant borrowed 1,00,000 from the father of the plaintiff as a hand loan about 5 years back.the plaintiff was demanding the interest 10/- per hundred at compound rates and due to financial crisis this defendant could not discharge the above said hand loan. The plaintiff and his brother along with their followers went to his village and insisted this defendant to discharge the handloan amount together with accrued interest or to sign on blank promissory notes.As there is no option open to this defendant,he signed on 6 blank promissory notes.Infant, he did not borrow any amount as shown in the promissory note either from the plaintiff or from his brother. The alleged scribe and at testers of the suit promissory notes is the kith and kind of the plaintiff.The plaintiff and his brother must have filled up the blank promissory notes subsequently and filed this false suits with a view of grab money from this defendant. The promissory notes are devoid of consideration. The allegations made in the plaintiff are hereby denied and the plaintiff is put to strict proof of the same. So dear laywers I request you, we are framers and earned that money purely based on the agriculture. What are the issues comes in this case and how tackle those issues to be sucessed? Please give your valuable suggestions how to win this case ? Thanks Advance....