Brother is forcing us to sign over property that we got in will

Right after my mother's death, her property and business were divided amongst us 4 siblings through a will. My brother is a drunkard, separated shrewd who blackmailed my sick and dying mother to sign over a large share to him by threatening public humiliation and harm to my father, sisters and my family . In return, he promised to not ruin our reputation and provide expenses for running the household. He also has several cases pending against him by his wife in the high court. He is currently occupying our house and has started to threaten my father and sister living at their house to transfer the rest of the property, threatening physical violence, harm to reputation and that he will go to his wife and ask her to pursue false cases on us. We are Hindu. He is constantly harassing us with threats and also spreading false claims amongst our relatives. He never once took his mother to hospital and now, he is changing the story to make us look twisted. How do we protect ourselves & home?