It's never accomplished anything for me. Just feeling more panic and anxiety when I experience their reaction. I'd say check your motivations for telling them. Are you wanting to tell them for you, or for him? What do you seek to accomplish by telling them? To control the outcomes? To show them you are not crazy? Because you know in your heart he is going to bash and badmouth you to them when he gets there and you want to tell your side first, or show them how good of a person you actually are before he fills their heads full of lies about you? Because those are the things that go through my mind when I've talked to X's parents and family.