his addiction is not your fault, and it never was. you had good reason to be scared of any outcome regarding any decision you made, telling or not telling, because you found an enormous dark secret that was screaming Danger!.
it's a learning process for every single one of us. No one can really say if you should tell your brother or not, that is up to you. you said he has been in recovery for 2 years? i would think he would understand enough about his addiction at this point to be able to talk with you about it.
you can't cause an addiction, you can't control an addiction, and you can't cure one either. but i think it's good that you're aware of you're feelings and wanting to get things to where you feel ok about it.