How to resolve constant disputes over our family business?

My grandfather and mother (an eye surgeon) started a business from scratch 23 years ago. My father (a civil engineer) joined the board a couple of years later. Today, that business has grown and my mother, father and uncle are Directors on the board. My grandfather was the M.D abd he passed away without leaving any will. My uncle and grandmother forced my father and cheated him into signing documents that gave my grandmother 92% of the shares and the rest divided into my uncle and my dad each. Now, everyday, my grandmother and uncle come and pick fights with my parents at the hospital, scream obscenities at them and try to bully them into agreeing with my uncle's investment decisions. My parents were harassed by my grandfather before he died on similar lines, and they have had enough. They want to continue working at the business without the mental harassment and drama. They would like to pay off my uncle but he demands that he give us money worth my grandmother and his shares. My grandmother is openly supporting him and my parents' health has worsened because of this constant havoc. I want to know what legal action they can take on my grandmother and uncle, and resolve this issue once and for all. On another note, my grandmother and aunt used to cut up my mother's and my clothes, steal our footwear and make threatening calls to us and my other aunt, and forced us to leave the family home. I myself heard my grandmother 's voice on the phone talking to me and threatening to kill my mother if she didn't 'fall in line'. My parents are not devious people and just want an end to all of this. What do we do?