Son blackmailing parents of committing suicide

My brother has been mentally torturing my family since many years. He wants my mom's house to live there only. My mom allowed for some years and recently found out he indulges in all bad habits. So now he is living with us. He constantly threatens to kill himself. My parents fear him and whenever they try to talk to him he threatens them of suicide. Says things like "you'll find my body tomorrow" and then my parents back off out of fear. He even drank phenol once only to threaten them. He does acts like not eating for days, running away from home to get what he wants since almost 10 years now. He has also been emotionally torturing me all these years by blaming me for all his acts that he is doing xyz because of me. My parents used to believe him and scold me until recently. Now they have understood his intentions but as parents are helpless and extremely afraid of him. They are even afraid to say anything to him because they think he might go and kill himself. What can I do?