Well, the young often do not see mental illness until they are independent and on their own. And the mentally ill are often much stronger than normal people. They tend to be the leaders in a nuclear family.
My mother was mentally ill. Borderline personality. Narcissistic. It was utter hell living with her.
And true to what you wrote, she ruled the household. Even over my father.
I didn’t put the whole picture together of her sickness and the effects until I was past 30 years old.
It is devastating growing up with a mentally unstable parent. You are correct, that kind of parent will drain you.
Can a kid overcome it? Of course. I just wish things were different.