Honestly, I’m not sure what you should do. I’m not sure about your situation but you do care about your family and siblings…. They can be dumb at times. I suggest talking to an adult you trust about the situation, someone who been there for you for a long time. I know that doesn’t sound like much and to me I have isolated myself from my family when I was in a rough spot and it led to my mental health getting worse (mostly because I had no one to talk to by myself. Kids bullied the bum out of me)
But talking to someone you know truly loves from you and has supported you and tried to help you become the best version of yourself, I suggest you talk to them about the situation. I also suggest if you have multiple sibling ask your other siblings, unless you’re the oldest, about the situation if they’re old enough to understand— like an older sibling.
I can’t say much as I have trouble understanding things outside the bubble my parents made for me and my siblings- but I’d try my best to figure out if your sibling truly meant those things. I have siblings who have said stuff like that but they never mean it, they’re either repeating what they heard or they themselves are going through something.
Other than that the best I can say is try and keep your distance from now until things cool down. Again I can’t say much since I don’t know much but talking to someone that loves you can really help. It helped me when I was having these thoughts and I hope it can help you.
If you need anything at all just ask