Being witness in WILL makes daughter deprive of right

As per the facts stated by you, the daughters have no right.  If they file any case or challenge the will, they will be in the loser's end.  Better they can compromise any problems with the father and brother and receive some amount.

A Will must be attested by two witnesses who must witness the testator executing the Will. The witnesses should sign in the presence of each other and in the presence of the testator.

Under Parsi and Christian law, a witness cannot be an executor or legatee. However, according to Hindu Law, a witness can be a legatee. A Muslim is not required to have his Will attested if it is in writing.

Since, the father has got the property out of partition of ansectral property he has no right whatsoever, to will the same to the son, as per the Hindu Succession amendment act, the daughters have equal share in the property. You have every claim over the property.

i agree with Vishal Ji,

since father is still alive and the will is to probate only after his death, better u challenge the will and seek injunction on the ground that you were forced to sign blank papers which were later converted into will.

I agree with Vishal and kiran.

 Can the daughter lodge a complaint with the police that her signature has been obtained by coercion?  Will such a complaint stand her in good stead when the Will comes for probate?