My wife's father mostly failed her, spectacularly, during childhood. She's a better person than me, because if my father had done the things he's done to her, I'd have nothing to do with him and would be indifferent to his death. Not out of hatred or something, so much as self-protection.
But now that he is old and more or less toothless, she has forgiven him and let it all go and as much for her own peace of mind as his, has normalized things with him and her monster-in-law. That doesn't mean they are much in touch, or that she trusts them, but it means she has taken back her power and allowed the relationship to be what it is able to be, which is basically no different than that of an old acquaintance. It works for her, and I admire her for it. But it's not something everyone is able to do before the end. And that's okay, too.
It also doesn't mean my wife won't have VERY mixed feelings when he dies ... and that, too, is understandable. Be kind to yourself and you'll get through it.
This is pretty much where I'm at. I've kept peace so that my now grown children knew them...my grown children see all the problems without me ever pointing it out to them but at least they know where we've come from and, like me, they do better. Sometimes an example of what not to do speaks more than all the telling them what they should do.