Do you feel you’re obligated to take care of your siblings once you make it? I’m not doing it. I don’t care what they going through. That’s why my mom

You have it wrong, she is in first position, you are second. She doesn't have you on her paperwork because that is her choice, and you have inherited it, so now you also do not care.
It's like when a kid is abused by their parents, when they have kids they will abuse them, it's an inherited learning thing.