There are people in my family that we visit occasionally, and for not too long a time, on the theory that we don't expect them to be any different than they have shown us that they are. The grandfather who is a pathological liar and who rarely keeps his commitments to be where he says he will be without making up some outrageous excuse (I have food poisoning! My GPS couldn't direct me properly to [National Landmark]! etc) will be invited somewhere to meet us where we will enjoy being even when he doesn't show up. We remind ourselves that his inability to show up is not a reflection of us or how much he cares about us. If he does happen to show up, it's with gift cards and he takes us all out to eat and we have a great time and we're happy to see him. The other grandfather sounds a lot like your father, who makes biting and mean comments regularly, then acts surprised when you call him on it. He does not do this to the kids in the family, only the adults, usually when the kids are not around. I have found that when I expect him to be biting and mean, it's a whole lot less painful when he does it. I don't think I"m immune to it even after years of this strategy, but it's a lot better to be a whole lot less reactive to it.