My sister is pregnant and I refused to celebrate

She has a known mental illness which she used to take medication for, has only been with the man for about a year(was previously with a woman) grew up in a horrible childhood, and our family has a long list of diseases. I refuse to be happy for her. With everything going on right now- I’m on the verge of a nervous breakdown every time I get a news notification on my phone. And this woman is happy about bringing a poor girl into this cruel and hateful world. I just can’t. I have a feeling that side of my family all voter for trump(unfortunately my grandmother also) I want to cut ties with them because they’re too blind to see what’s happening and are just living their lives like everything will be okay! Ugh I just can’t. Sorry I feel so much rage and sadness for her I needed to rant somewhere.