Dear Sir,
Yes, your father can file suit for declaration for cancellation of such sale deed. It must be said that the fact of fraud come to light very recently.
Section 31 to 33 of the Specific Relief Act, 1963 provides for the cancellation of instruments which reads as under:
When cancellation may be ordered:
(1) Any person against whom a written instrument is voidable, and who has reasonable apprehension that such instrument, if left outstanding may cause him serious injury, may sue to have it adjudged void or voidable; and the court may, atits discretion, so adjudge it and order it to be delivered up and cancelled.
(2) If the instrument has been registered under the Indian Registration Act, 1908 the court shall also send a copy of its decree to the officer in whose office the instrument has been so registered; and such officer shall note on the copy of the instrument contained in his books the fact of its cancellation.
Dear Sir,
You can fight by yourself as your is died.