Right of a father of 3 daughters in family businesses & property

My father are 4 brothers, And only he has given birth to 3 daughters (2 married & 1 unmarried) and no son. Rest other brothers have atleast 1 son. My father has been running 2 of the family partnership business single handedly from past 30 years. Just after marriage of first daughter , my grandfather and 3 uncles started torturing my parents for leaving the control of business. So, he left management of one of the business (though till date has share of 40% in that business) and was focusing on only one business (herein also he has 40% share ) from past 3 years. Now my uncles are torturing my parents again and forcing them to sign a documents wherein he shall withdraw his name from all other places but in return he cannot get any business in his name completely because he doesnt have a son to carry on that. Therefore, my uncles are torturing them everyday by interfering in one business , and they say that they have a right to interfere as they are partners in that business. My father is also a partner in one of my uncles business but he never interfered in his business from past 30 years. Please suggest