Hi Pea8 and welcome to our online community

It isn't easy for a child growing up with a BPD sibling. This can really affect people long into their adult lives. Based on what you've shared, you've clearly also been very much affected by the interactions with your brother.
When you were younger, how did your parents view your brothers behavior? What did they do when your brother was misbehaving and mistreating you?
You are now an adult, but like many of us, you realize that you have certain struggles related to what you've been through growing up.
Have you ever gotten any support to help you deal with your ow struggles?
We have a resource here that is very helpful for adults who suffered childhood abuse:
Survivors' Guide for Adults who suffered Childhood AbuseThis guide helps us assess where we are in our healing, what issues we are currently dealing with, and how to move forward from here. The guide takes us from survivor to thriver though 3 main stages: 1. Remembering --> 2. Mourning --> 3. Healing.
Each stage consists of 7 steps. The healing process described, isn't necessarily linear though, in fact often isn't and we will often find ourselves revisiting steps we had visited before.
When you look at the guide, where do you feel you are right now?
What would you say are the main elements listed that you find yourself most struggling with?
The Board Parrot