Good Morning Tammie,
I don't think that reaching out to your brother is codependent behavior. I think it might be helpful if someone in recovery would visit him. Then after you make the contact with the AA group you can try to let go of the results. It would be codependent to try to "force" this alliance. If it happens, great, if not, perhaps his higher power has another plan for him. Perhaps your idea is the plan. I say take a chance. I am sure the others will be by with helpful insight. Have a goof Friday and keep the faith.