I liked Frankly's idea of getting social services involved.
His chances of moving on to harder drugs are far greater with a meth using mom and alcoholic dad.
They might be able to get your brother into a rehab situation or have him made a ward of the state.... not the best situation, but it has to be better than the one he is in.
My heart goes out to YOU, and I know you don't probably want to hear this, but getting YOURself to an Alanon/Naranon meeting can help you brother in the long run.
(((Patriot)))