Once gift deed is executed duly stamped and registered your brother would be absolute owner of the house
2) if your mother was forced to execute gift deed she can file. Suit to set aside gift deed on grounds of coercion
3) seek injunction restraining brother from creating third party rights on the flat
4) in alternative move senior citizen tribunal to set aside gift deed
5)being married does not disentitle you to inherit property on mother demise intestate