Welcome
Littlebeetle!
How thankful I am that you've come to find us here and share some of your story with us!

There are many other members here who have a BPD sibling, and such stories they can tell! Similar to yours, there is so much hurt when a sibling attacks you. I am so sorry. Thank goodness you were able to get away for a time and begin the healing process which in turn sounds like it helped to strengthen you. However, it doesn't take long for the triggers to send us right back into chaos, does it? I get that and frequently walked that road with my uBPDm.
It is really good that you are concerned about your nieces and nephews. I wish I had someone in my life who would've been aware of what was going on and who cared. I sadly speak from experience when I say that as children, whatever the environment we grow up in, we see it as "
normal." It took me several years of T to wrestle with the word 'abuse' and wrapping my head around it before I could comprehend that yes, I was very abused and my siblings as well. You have also walked through your own abuse with your sister so you have the ability to see what she is beyond the appearance others may see. Just because this may appear normal to them does not make it normal, and there are things you can do to support and show that you love and care for them.
I am going to post a link to a workshop that has been most helpful to me and that will give you some very good ideas of what you can do. There is a ton of information in the workshop so please don't try to read or absorb it all at once. The link will be there for you to return to and thoughtfully ponder what is there.
When are the children of a BPD parent at risk? How far away from the children do you live right now? How many children are there and how old are they?
Looking forward to hearing back from you!
Wools