Dear Katie,
I have read some of your previous posts. The thoughtfulness that you express in them is very impressive. You are right in your desire to support him but it is probably better if you can also seek professional help for your brother.
Problems that are deep rooted require time, effort and expertise to be sorted out. How does your brother see you? How willing is he to take your support? Does he have the realization that you seem to have?
These are the questions that will probably help you in understanding your role in his recovery.