Can a gift deed be cancelled or revoked

My father expired without making any will . a week before my marriage which was an intercaste marriage my mother and elder sister forced me to execute a gift deed in thier favour releasing my 1/3rd share in my late fathers flat . i excuted the said deed and also went for registration as they threatened mt that if i would not excetue the same they would not attend my marriage and would make sure that other family members also would not attend . hence i ahd to excute this deed just a week before my marriage reception . two years after my marriage i learnt that my mother and sister are trying to get the flat transferred in thier name with the help of a copy of the gift deed , the original gift deed is in my possession , they also cheated me by stataing that they would mention in the deed that i would be compensated for my 1/3rd share which im releasing in my father flat through other means but after signing the document i was surprised to see they have mentioned that i have released my share to them out of love and affection . i have filed apolice compliant against them for cheating and coercion and also filed a case for cancelation of the deed in the high court. i have also written to the society asking them not to transfer the flat as its in dispute. can any one advice on this matter to me . all your suggestions shall be highly help ful