Have you told this to your therapist? What does s/he suggest?
There is no reason to believe this guy has told your brother the truth about anything. Unless it serves some purpose to appear desperate and pathetic, most alcoholics are pretty good at hiding what's really going on in their lives. It's not impossible, but I find it pretty improbable that he's had an epiphany and is really doing that great and that he's now sober and stable, much less "amazing." You already know he's a liar.
I trust you've told your brother not to give you any more "updates"?