Since father has executed gift deed in your favour duly stamped and registered you would be absolute owner of the property
2) you don't have to give any share in sale proceeds to your siblings
3) your siblings ought to have filed suit to set aside gift deed on grounds of undue influence or coercion which they have not done
4)you have not mentioned how your father got property share of plot from grand mother . The source of funds for purchase of property by grand mother . Kindly clarify