In many ways my kids were lucky. My mom married her second husband when my youngest was four. The marriage lasted for fifteen years, so it was apparent to all of my kids that it was best for grandma if she left ‘name withheld’ who they never called grandpa after they were about six anyway.
Really by the time my youngest was twelve she was asking why Grandma stayed with him. So it was a different case altogether. We could all see it was a bad situation but my mom couldn’t.
Ironically when my wife and I decided to divorce recently, the first question my youngest asked me was ‘what took you so long?’ My kids are more perspective than I am, maybe they will have better luck with relationships?