I’m so sorry you’re having to deal with this, but you’re on the right forum as it’s a familiar struggle to folk on here.

…. I accessed trauma counselling, enrolled back into education with a career and for the first time in my life, I started to put myself first and it’s something that im still continuing to do.
Good move. Your post suggests you have emotional intelligence which means you’re more likely to “burn out” than someone with lower to no emotional intelligence, and more likely to want to help others, so notice the team / family dynamic.
You mentioned you’ve gone back to Education, which encourages us to reflect and continually improve. That’s harder if you lack emotional intelligence, seemly impossible to some with a PD , as they assume everyone thinks the same, so talking about anything is just manipulation.
During this time, my sibling accessed mental health services and recognised the damage they had done to my parents and younger sibling.
Great news, it suggests your sibling is capable of change. It’s worth noting that PTSD and BPD have overlapping symptoms. Also C-PTSD can occur slowly over time in certain “chaotic” households, so can go unnoticed until you “burn out”.
I’m really in limbo .... I don’t want for them to kick off at me for being honest with them ...
“If convinced against your will, of the same opinion still” meaning, if someone is still angry about the past, that needs addressing before someone can move on.
But it does sound like you and your siblings have made good progress, but at different speeds and in different ways. “Guilt” is healthy, but folk with a PD will be able to manipulate you using “shame” so knowing the difference is important.
I’m not on here regularly, but didn’t want to leave you hanging. Others will chip in, and different folk need different strokes, so feel free to ignore my advice if it doesn’t click. But it worked for me and my siblings.
