It is such a shaming thing to be rejected that one always thinks they are the only one it has happened to. People expected for you to be the one thats rejected that you are the criminal, abuser or something, not the only one out of 5 siblings who is actually quite a good person
THSI!!! ^
I am in the same position as you, and like you I feel ashamed when I should have no need to. I rarely tell anyone that my three siblings won't have anything to do with me, because like you, I can feel them thinking that I must be the Evil One.
I don't want to go into what is really horrible detail, but we had dreadful childhoods, and I especially because I was the family scapegoat. I've learned since that this is very common - for a dysfunctional family to have even a semblance of functionality, a single individual is blamed for everything that happens that is wrong. It was me.
Perhaps it is the same with you, too - I don't know, because our family situations are different - but it can lead to this one person (who usually does everything in their power to make things "right" - as I did, and as it seems you did, too) being kept on the outskirts all of their lives.
This enables the others to have a common ground of complaint, which helps them to keep together. It's a survival mechanism for them, but it doesn't make it any easier to bear.
I have learned to let it go (most of the time), but like you, I dread learning that one of them has died, and I am the last person to know. It would break my heart.