From reading your post. It sound like it will be more of an immigration visa then a visitor visa you are seeking and that is probably how the consular looked at it too.
A visitor visa has nothing to do with your bank account or tax returns. Your Brother and or mother needs to show proof on their own, that they are only coming to the USA to visit and that they have ties to their country that they need or will want to go back for. Examples Family, bank account, owning business. They need to show that is more beneficiary to them living in their country then it will be for them to live in USA.
With you being a USA citizen and your father having a green card that show more of intent to stay then just to visit.
