How to accept sibling estrangement

I would love some advice on how to accept estrangement with my siblings. In brief, my brother and sister decided about 2 years ago to stop speaking to me. My mother told me this is because they don’t like the way I treat her. Neither her nor I think I treat her poorly, though we do fight when we’re together too much (which is like once every 2 years and the fights are nothing more than short lived yelling arguments). I also am not completely sure I have the whole story here as my mother tends to stir the pot and also likes to put blame elsewhere (I fear she has painted me as worse than I am to my siblings). My mother and I have had a fine relationship this whole time, though I do keep my distance for these reasons.

This is bothering me now for two major reasons: 

1 - I can’t help but feel like my siblings “threw me away” over something relatively small. I hear about siblings who have each other’s backs even with super terrible things like murder and pedophilia (like R Kelly’s brother). I have a lengthy history of romantic relationships ending badly and this is contributing to the feeling that I am “disposable.” This feeling is now leaking into other areas of life, like I don’t want to spend time with my parents because I feel I am so disliked and I don’t want to pursue a romantic relationship because I am such a terrible person.

2 - I can’t shake the feeling that they have been given bad information. They never gave me a chance to discuss this before they decided to cut me off.  My brother and I have never been close but grew further apart in adulthood because of differing political beliefs, but my sister and I were close and it was an abrupt cut off.  She simply said she wouldn’t talk to me anymore until I fix my relationship with my mom. I have spoken with my mom at length about this and neither of us know what she’s talking about (other than the rare fights that neither me no or my mom think are worth ending a relationship over).

I would like to be able to simply accept the fact that they have chosen to not be in my life and move on without all the guilt, shame, and confusion.  Any advice?

Note that I cannot speak to them. They will not engage.  My mother will talk about it and essentially puts the blame on me while also being confused about their choices. My father will barely acknowledge the rift and likes to pretend all is fine and well. Speaking to any of them (or attempting to) is not helpful.

Also, for context, my siblings and I are in our 40s.