That is heartbreaking. Thank goodness you were around to pick up the pieces for your brother. He sounds like a saint!!! He can hold his head up and say he tried his hardest and put your mother first. Not many of us would do it.
She sounds similar to my mother. . Remember she is an alcoholic and a Jehovah's witness - a truly frightening combination. Don't blame yourselves for how things turned out. You've done more than a lot of kids would have, in the situation.
Take care. Let us know how it works out.