My buddy dated a BPD with 2 kids. He fell in love with them all. The kids started calling him daddy and all that mess all while she is still legally married. Then she dumped him over something silly and started seeing a new guy within a couple weeks. Now she posts pics with the new guy and kids going on vacation like its their father when they still loved and asked about my buddy. Needless to say, the father of the kids has had enough of her toxic behavior she brings onto the kids. He's hired a lawyer and plans to finalize divorce along with trying to take full custody.
I'm no longer surprised by BPDs behavior, but the crap they put their kids thru is beyond disgusting. Hell, I saw a BPD chick on a BPD forum who was posting pics kissing her 7 yo son with open mouth, putting lipstick on him and kissing him like it was a normal thing to do.
Exhausted, I know how much pain you're in over this, but you are doing the right thing by staying NC. Deep down, we want it to work with them more than anything in the world, but after being away from them for weeks, we are able to finally realize just how crazy/toxic they are. Even if you went back, things would feel amazing at first, but that will quickly change in a matter of days or weeks.
Like you, I miss the get together's with her family. She always told me I was the only man her dad her ever liked, her mom adored me, her brothers were like my own. I formed an amazing bond with them, that was something even 10 moths out I still dwell on a lot. Partly due to my family being a bunch of mental hermits who I've never really enjoyed being around nor do they do ANYTHING fun. They basically sit on the couch all day long, haven't taken vacations in over 25 years. They are basically dead inside.
Crazy how deep she got me involved with her family, sleep overs at her parents house, BBQ's, helped them move, golf, traveling to other states to meet her grandparents and other family only to destroy it all. I can only imagine the BS she spread about me and the real reason it ended as some of her family used to call me on the regular, then the calls just stopped shortly after she moved.