I have 6 brothers and a sister - 2 brothers have an issue (both I suspect of drinking problems) - 4 other brothers and sister - no problems - mother and father - no problems - all of my friends - no problems.
A saying we have here: Don't go to the hardware store looking for bread. These two brothers don't like your wife, they've told you so, and they've ignored your pleas for peace. Your next step is to believe them, and to avoid conversations or contact with them that leads down the road to Crazytown. No more counseling requests, no more well-meaning phone calls looking for resolution, no more pleading why, why, why.
That hardware store doesn't have bread.
Or, what I say about my mom when it comes to me wanting to feel validated and loved by her: That well is dry. I have to stop going there when I'm thirsty. I have to fulfill that need in other places. I can go to that well for other things but it doesn't have water. I have to get water elsewhere.
Your brothers are no longer a safe space for you. If they are indeed alcoholics, they never were. It's fine to behave in a way that acknowledges that truth. It's also fine to have a marriage that is not sanctioned and blessed by them. The nice thing about being grown is not having to have their permission and approval to live your life.