Maybe your brother will see the light while in rehab. It's possible. But no matter what he does, there is plenty you and your parents can do to make the situation better when he comes out of rehab.
See if you can encourage your parents to go to Al-Anon or Nar-Anon with you while your brother is in rehab. It would do all of you a world of good to start working on yourselves. Your parents are enablers, but maybe by attending a group they can come to see what they have been doing all along and change. If not, then you will have to let it go as you can only control yourself--change yourself. Get the help for your own sanity so you can learn a better way of relating to your addicted brother.