[Order of events]
My mother died in overseas due to a medical issue. At the time all the family properties was under my mother's name which my father paid for it in cash. I, two sisters and a brother signed the “release deed” under court of law for my father to take control of all the family properties but another brother(last sibling) didnt sign it. My father gave me a house under sale deed for the money I solely paid for my mom's medical expenses.
Now after 10years, due to unsound character, my last sibling has made privately a release deed through the local town Thasildar for my father and made my father give him a settlement of a commercial building recently which was done secretly. The settlement has a line called irrevokable in it. My question is; is it possible for that settlement to be nullified since my father is unsound and settlement done under coercision. And can I make a claim against the building even though I have signed the release deed previously along with my other siblings because my father verbally assured me that I would get the commericial building. My other siblings are getting a share of other properties through a registered will; therefore I have been made a fool for not getting any share of my own. Please advice.
