Well then follow the Buddhist philosophy of "the best thing to do in some situations is just do nothing." It sounds like you are worrying about a lot of "what ifs." There's no way you can forecast the future of what your relationship with your brother will become. And no one here can do that for you either.

My brother estranged himself from me after I set boundaries with him, because he did some very abusive things to me and didn't like it, when I confronted him asking him to take responsibility for his behavior. I cannot allow ANYONE into my life who refuses to take responsibility for their actions. He always hides behind God as his justification and uses his religion as a convenient excuse for his horrible behavior. That is something I will never tolerate from anyone -- let alone a family member.

I will say this: if you want to permanently estrange yourself from your brother, you can email him or call him and tell him why you are estranging yourself. Or, do nothing and leave things the way that they are, and play the "wait and see" approach to how you feel when the next birthday or holiday comes around.

Sibling estrangement is nothing taboo. Its actually quite common. It feels weird to discuss because society treats it with kid gloves. Family and sibling estrangement is a common occurrence yet society won't acknowledge this. It's quite healthy to separate yourself from toxic family members. Nothing wrong with doing that. The adjustment period is the emotionally painful part, because you have to endure your remaining family member's criticism and judgement and personal attacks against YOU for having healthy boundaries.

You have to set the boundaries and you have to be the one to maintain those boundaries with your brother. He can't do that for you. You have to do that. And that's the scary part.