1. Well when the property was partitioned then your father had 1/3rd share in it along with you and your brother.
2. You are silent whether your father at the time of his death made any Will or any other bequest in respect of hs 1/3rd share.
3. If no then his 1/3rd share is to be equally divided among all his legal heirs which include you, your 2 brothers and 2 sisters and your mother.
4. Accordingly your sisters and left out brothers acquired 1/12 share in the property and hence it would be natural for the bank to ask for NOC from them.
5. If before death of your father he transfer his share to your mother through a gift deed then only the sisters or brother can be restrained from claiming their share.