Succession certificate

The deceased was staying in mumbai, on the way to native he was directly admitted to hospital due to emergency on 3rd july 2015 and expired in the hospital on 06th july 2015. however, the sisters declare that the deceased was unmarried but one of the brother has seen one sbi life certificate where in he has declared his status married and mentioned spouse name. the deceased has left certain bank fd not more than 15 l as of now, so the sister is in posession of the fd and original sbi lifecertificate concealed by her husband to the deceased brother. whether sucession certificate can be obtained by the deceased sister if the brother of the deceased does not join with them for obtaing sucession certificate. the deceased was staying in oldage home in mumbai before hospitalisation after his retirement from 2010 t0 july 2015 the sisiters of deceased wish that the deceased brother to join them and obtain succession certificate to claim right on fixed deposit by telling lie. how is it possible to get sucession certificate by the deceased sisters? please advise sir what should i do ?