I write the letters to the people that don't get it and never send them. Basically, you gotta take care of you. It's a cold hard fact of life that not everyone is as empathetic as you would be, or you would like them to be. So put yourself first, and them second. Enjoy them for what they do offer, after you've taken care of yourself.
My family is THE WORST. I have one aunt that gets it. I'm one of 4 kids and have 6 pairs of aunts and uncles and only 2 sane ones. Look to the sane ones, don't try to force the relationships that aren't there. Think about it, you know what's working, what isn't. You're not alone, don't put all your eggs in that one basket! Vent here instead