This history of your mother that you are describing is just awful. Her treatment towards you is most likely how she was treated where she was emotionally abused and clearly was abandoned. What can also happen is these people that raised her/ housed her may have told her their abuse was love too.

Remember, people with NPD are not born that way, they are definitely created to become that way from how they are raised. They don't really "know" they have NPD either, all they know is it is how they survive.

What I have noticed is they typically pick on the child that is the same sex they are too. They even consider it a threat/competition and as in your case she had both males enabling her to put you down and make sure no one else adored you or cared about you. It is better for you if you keep your distance from her nest where she prefers to have her two males doating on her and feels threatened when you are around.

I have seen people do things I could never understand. I have talked about a neighborhood I lived in where other women acted very strange towards me and they did not even know me. I thought they were the rudest people I had ever met and I grew to hate that neighborhood and felt it was very unfriendly. I wish I had a better understanding of "why" these women were like that too so it did not upset me so much.
Bullies are narcissistic too, it's all anger = fear based. What always surprised me is how they tend to develope a group of "enabelers" around them too. That is what really got me because I could not understand how their enablers would chip in and be mean to another person without recognizing how wrong it is. Yes, it does bother them to see their victim do well or thrive too.

Just understanding or learning about it is helpful but it's hard to emotionally heal from it. Surprisingly, there is a lot of this taking place in society so it is a problem that happens a lot. There is definitely a lot of it in the political atmosphere too.