Yes, I have a sister who only talks to one of our brothers on occasion (maybe 3 times a year at best) and from what he tells us, she refers to our parents by their first names, not "mom and dad". She also has threatened our brother that if he ever tells anyone about what she is up to or where she lives etc... she'll stop talking to him too.
For me personally, I lived so many years with her always needing to be right and her always trying to make it a point to be "the black sheep" of the family and not to mention the countless fights over literally, everything....I've finally realized, I for once have a sense of peace in my life. It's sad that I feel this way, but to not have such a negative force always crowding to me is uplifting, it really is.
As far as my kids, they weren't born when she was in my life so she's never met them. I don't talk about her to them either. If the day ever comes that she finally tries to make things right it will be up to her to apologize to my children for being such a bum aunt.
And for my parents, oh Lord have they tried. My mother has helped my sister in so many ways and bent over backwards to pull favors etc... that my dad finally said she needed to step back because all her efforts were clearly not working. My parents tried to even meet with HER counselor on her turf (another state) and when my parents arrived in California, HER counselor got really rude to my parents and then my sister didn't even show. My dad was so flaming mad after spending the money to go there and have it blow up in his face that he stepped out of her life and told her when she was ready, she could come back and he'd always be there. My mother on the other hand, she continues to send her a birthday card each year but that's about it.
I've learned that once you raise your child into adulthood, you really can't control anything beyond what they are going to do, outside of an alcoholic intervention I suppose. It's very hard to see your family members struggle but see their stubborness as a road block in your relationship. But, don't dwell on it, keep moving forward in your own life and enjoy what you have. If your sibling decides to re-enter the picture in a more "normal" fashion, embrace it but don't keep brining up the past, just start at that moment and move forward, that is what I plan on doing if my sister ever decides to re-enter our family. If she does though, it will have to be on her terms, not mine or my parents.