I think we all have at least one stinker in our families, but EllyMae, I would not have 3 family Christmas dinners just because DH's sisters don't like each other. DH and I set the tone (and rules) in our home and each sister would be told face-to-face, if possible, that "we would love to have you but you all are invited. However, we expect each of you to be polite and pleasant. If you are uncomfortable with that, you may want to make other arrangements." Say it and mean it. We have a couple of "difficult" relatives but they don't pull that stuff with us. These two we just ignore completely since there is no resolution. However, when we see them at funerals mostly we are always civil and polite.