Cheated and blackmailed by brothers on propery

We are 5 brothers and parents died without any will. I was a govt employee. My 4 brothers did not give me a single rupee to me from farming for 35years when I was living outside, they ate my share of money also. When I retired I asked them to partition so that I can build house and leave my retired life, since I don't have any other property. They told to divide in ourself without court interference, mutual agreement. We did it and they let me to build the house after that without objection but after that they started blackmailing me for money. They already have taken 2lakhs from me to build a room and still asking for more money, clearly they have eyes on my pension. When I refused to pay more then they have filed a case against me. What to do? They have eaten up my share also for 35 years, took huge money from me to build their house and now seeking partition in my house also which I built after mutual agreement.