Torture from Brother on parents for property

Hello Sir, My case is a little complicated may be. It so happens is that I have a elder brother who is my mother's first child. She was married to a person who left her to marry somebody else when my brother was a 3 yr kid. She was also thrown out of the in laws house along with the child. They had no means of survival then. My father happens to be a younger brother to the man my mother was married to first. Seeing to their plight my father had taken them in to help them survive. Later in few years time when my mother was taken back home by her first husband that is father's elder brother, my father's friends suggested him to marry her as she would again have to leave if he married some other lady and she with her child would end up in the same plight. After marriage i was born and as i grew up i noticed tentions at home and now after 28 years my father just retired from a govt job last november 2016. Meanwhile my brother who is not my father's son, has made all his credentials like aadhar car voter card etc with my father's name on them as his father. now he has started torturing my parents for money and property claiming that as my father had brought them home so my father must pay is demands. he has hit my mother a lot times for money and creates a rucus at home every day. he threatens me, my father and my mother for money and property. i work at a private firm so i stay at a different place. today i heard that he has demanded for 10 lakh rupees and a 4 lakh rupees fixed deposit in his daughter's name in addition when my mother asked him to leave the house along with his wife and child. he refused and went on to hit my father on his back with a punch. i am afraid for my family and without any legal knowledge i feel very scared and helpless. the problem has increased after my father's retirement. i fear he might do something bad to them. I want to know how do i deal with this problem. Does he get a share in our property? this property is self aquired by my father from his job and nothing was inherited from my grand parents. he is my mother's son but not my father's child. he has forged the documents with my father's name on them but we have a school passing certificates of his with his actual father's name on it. Does he have any right to claim any part in my father's property? if he legally has any claim then we dont have any problem to give him his share because we dont want any quarell. PLease help me understand what and what not is to be done to get rid of this situation. We just want him out of our lives on way or the other because he has been given enough chances to redeem himself and do a job or any career of his choosing but he has never tried to do anything. he just wants to get the money from my father and doesnt want to work. after 44 years of age and a marriage and a child he doesnt even try to work. he earns merely 3000 rupees as he doesnot go to work regularly. all he does is create nuisanse at home and hit my mother time and again. I am deperate. please help me