Coming out as trans or gender-expansive to parents and family can be a very difficult task. You may already know that you'll receive a negative reaction. Or you may be unsure. It can be scary, depending on how close you are to your family. And there may be some members of your family that are really supportive, and others that aren't.
First, it's important to make sure you have good support around you before you make the leap to come out. Make sure you have friends and other loved ones who are supportive, and can help provide space for you if the response you get to coming out is negative. If you don't have this kind of support system, I'd suggest getting it in place before you come out to your family, unless you already know for sure you're family will be supportive of your decision to transition.
Depending on how often you see your family, and how far away you live, you might choose to send them an email, or come out over the phone instead of doing it in person. An email, alongside some supporting materials - articles and links to books and such, can be helpful. It gives them the chance to have their reaction not in your presence, and process it without you having to witness their initial response.
I came out to my elderly parents a few years ago, and was really surprised at the way they responded. They were initially hesitant, but became very diligent at using my new name and pronouns (when they remembered - sometimes they forget, but then correct themselves, and are also open to my correction.) They became very supportive.
But, unfortunately, that response to coming out is not universal, although it is getting a lot better. Again, having a good support system you can depend on is important, because you may lose your connection to your family because of transition.
And remember - it's not about you, even though it feels that way, and it hurts. It's about their fears, their biases, and their thoughts. You are still lovable and valid, even though they can't see it.