I’m gonna say NTA but I do hesitate to call your brother one. Your mom is tho. My family dynamic was similar to yours. My father is a narcissist and I grew up having similar arguments with him. Unfortunately engaging with what they say will not help. They won’t understand. They refuse to. Arguing with them will not help. You can’t change their mind. It’s difficult to find a solution while you’re living with her. People will probably tell your to just ignore her, but often times when you do that they’ll still get angry. The best thing you can do is just be pleasant until you move out. It sucks to do because a lot of times you just wanna yell at them to try and make them understand, but they won’t. You’ll be wasting your energy. Trying to avoid arguments while living there is probably the best way to go about it. That’s what I did. Then when I moved out I ignored him. Dealing with a golden child can be difficult. They often don’t realize what the family dynamic is actually like, but it’s important to remember that it is still a form of abuse to make someone a golden child. It’s just a different form. He’s still young, so hopefully he’ll realize. I wish you the best!