Its a little hard to tell from your post, but if he and his brother are saying this just to try diminish you/place the ball in your court/blame you - in some way -then I don't see the point.
I did individual and family therapy with my husband . In fact, family therapy is often recommended for people who are seeking to make changes in their drinking. And for the family member to share how the home, relationship has been affected by the behaviors.
It was helpful for me to be able to communicate calmly with the therapist there to sort of guide us. I was able to express a lot of things that I might not have been able to otherwise. My husband was seeking help for drugs and alcohol, but he was still drinking alcohol at this time. He was a binge type user also and alcohol was only a problem when he mixed with drugs. If a person is consistently drunk, depending on the severity, the way it affects the brain then it might be a pointless effort unless you are working with someone who specializes in addiction/therapy. That is what we used and what I would personally recommend anyway. Many doctors work with patients on moderation and not complete abstinence. Often people think they can moderate (some can, some cant) and there are reasons why a person may binge, etc. Different degrees of alcohol use disorder, etc that a therapist can share with both of you. The whole process can be really hard for a family member and sometimes its just not worth it IMO if there is not enough of the relationship foundation remaining. It also doesn't take long to find out if it will be of any value.. more than one session. I mean they even say to go to alanon l 6 times and different meetings to see if it might be of value.
If you are done with the relationship and feel content with your decision then I probably wouldn't bother. Id just try to move on with life and not look back.