1. IF the property was NOT purchased by her own Funds by the Mother (say property originally belonged to her late husband (your father), THEN Mother CANNOT execute any Gift Deed, in anybodys favor.
2. Check properly as to how the property came into being in name of mother. IF above point no. 1, is correct, ALL the residual Legal Heirs of the deceased Father (original owner of property) are entitled to EQUAL portions of the property. IF SO, You have a good case in Civil Court, by following due procedure of law.
Keep Smiling .... Hemant Agarwal