Procedure to legally Disown Parents

I will be moving abroad after 3 years from now for work after completing my education. A year after that my sister too will be joining me there and as soon as she moves from here, we both want to legally disown our parents and family. Our parents are verbally abusive to us on the pettiest of the issues and threat to physically hit us or to move out of the house if we disagree to them for anything, even if we are right. We have no liberty at all, they want to control each and every action of ours and time and again, on issues they try to take away the basic necessities they provide. They also threaten us of stopping our education and getting us married to anyone randomly if we dare to go against their wishes. The home atmosphere and our parents behavior is mentally very disturbing. After around 4 years from now, when me and my sister are financially settled abroad we want to cut off our parents and family forever.