I would get help from NACOA – the National Assn. for the Children of Alcoholics. This applies to adult children, btw. They run a free helpline and are really good. And there’s DrugFam who have more resources and will get back to you quicker.
The book I found very helpful (my dad had mental health issues – very similar to booze) is “Unspoken Legacy” by Dr. Claudia Black. It lays bare what happens when there’s addiction in a family, going back 3-4 generations. There’s also a spreadsheet to look at and complete, as often we find there are many of us in particular family groups. It’s in the genes. Because of the way my dad treated us, my younger brother and I both ended up with addictions: him drugs and me booze. Eric (brother) never made it out and took his life at 54. I quit drinking for good at 62, as it was wrecking my mental health. Now 70, and never felt healthier.
The substance misuser MUST want to seek help. No family, nor friends, can force them. It’s very damaging to force them. Check out the information on this site about boundaries: how to decided on them and how to set them AND the consequences of the person not changing. Not following through is also damaging. Sending big hugs.