I spent most of my childhood in an alcoholic home so I know some of what you’re dealing with.
Al-anon wasn’t around (for teens) when I was your age but I think that its really important for you and your brother to be able to talk to others who are walking in your footsteps so you don’t feel so overwhelmed and isolated.
The first thing to do is find the phone number for the local AA (yellow pages or online). The phones are only answered by others who have gone through dealing with alcoholism (not some bored answerring service operator). Be honest and tell them you would like to be able to go to Al anon meetings. They will most likely be able to arrange a ride for you since you don’t drive yet.
Unless you live in Outer Mongolia , there should be several groups within convenient distance. Whether its a teen or adult group isn’t necessarily what’s most important (since you’ve been a member here for awhile, I’ve read enough of your posts to resize that you are extremely intelligent and mature for your age and fit in fine with adults)
What’s important is that you find a group that you feel comfortable with. Trying to deal with your parents alcoholism is tough and you don’t have to feel so alone. Others have gone through and are going through exactly what you are and are usually very welcoming and helpful to newcomers.
As far as dealing with your parents, I hate to be blunt, but alcoholism is a disease of denial. Every attempt to face them with reality will likely be met with denial and minimizing.
This will be the likely response when your cousin confronts them as well.
But at least you have one family member that you can confide in.
Just realize that in 3–4 years you and your brother will be out of the house either in college or working.
I would also suggest educating yourself as much as possible about what dealing with alcoholism involves. There are many good books out nowadays with accurate helpful advice that I wished had been around when I was in my teens. (Feel free to PM me and I can hunt up my list for you ).
Although it may be possible at some future time to stage a planned intervention with the help of your cousin and other family members, the most important thing right now is for you to find some support. Obviously it’s not something you normally talk with your friends at school about, so its important that you find others with whom you can share and ask questions, others who are going through the same stuff.
Please don’t blow off the suggestion of Al anon. It can be helpful in ways you can’t even begin to imagine. Make that phone call soon. I guarantee you’ll be glad you did (and if you’re not, you can yell at me in PMs and tell me why :)