Just to add, your parents shouldn’t be constantly burdening you with their crap. They are grown ups. This goes along with what @LuckyGuy wrote about you being an adult. I don’t want my mom to hide from me if she has a terminal illness that she is getting ongoing treatment for, but she didn’t bother to tell me every time a small little skin cancer was removed, and that’s just fine. It was a nothing, taken care of quickly with an office visit. I don’t know every time my mom or dad has a medical procedure done, and they don’t know when I do. My husband’s family, his parents always tell, because they always assume they are dying. It’s ridiculous.
If it’s financial issues, if you can help and want to help, then fine, but if you aren’t in a situation to help, then they need to handle it without burdening you.
If it’s a dynamic between your parents, their relationship, or with your younger brother, try not to get intertwined. I’m entwined a lot of the time and nothing good comes from it. I don’t have the addiction stuff to worry about, thank goodness, that just makes it all much worse.
What I have noticed about many addicts (not all) is they carry around pain from childhood that makes them insecure and angry and there is very little you can to for them. They will suck you dry, because they are so needy, manipulative, and dependent. Like I said, not all addicts fit this generalization. Some addicts are purely physically addicted from circumstance. I’m not assuming anything regarding your family.