If you hadn't already mentioned that you had a younger brother who could do no wrong, I was going to ask if you were an only child.
As it is, you've answered it already, and it's instantly clear that you are the family scapegoat and he is the golden child.
It's also apparent to me that your mother has set herself up in the role of rescuer - she gets to tell anyone who will listen that she is "always having to step in and rescue the children while Smith is out bloody drinking again", putting you down and elevating herself at the same time. Playing the martyr role, poor her, look how hard done-by she is, having a drunk for a daughter!
You doing good things for anyone completely goes against her internal picture of you, and, as a narc, she cannot possibly be wrong about you or anything, so how very dare you show personality traits, and do deeds, that are totally foreign to her picture of you! No wonder she gets angry. You're messing with her head!
I'm so sorry that you have a mother like this. I'm equally sorry that your father enables her, makes him as bad as her. I don't know what your relationship with your brother is like, or what his relationship with them is like; but if he's still tight with them and thinks they've done nothing wrong, then it might be better to go LC or even NC with him too.
No, you can't fix this. You didn't do it. SHE did. You can't change her, you can't change her behaviour, you absolutely can't change how she thinks about you. The only thing you can change is how you react to her batshit behaviour - and under the circs, I think you going LC, possibly NC, is probably the best way forward.
