In my family, there were three children, and I'd say we ended up in sort of a three-way split. I am the eldest, and my NM's target. I'm no saint, but I did grow up to be a do-gooder. I'm the one who adopts all of the animals from the shelter, gives way too much money to charity, does free work for people when I can't afford to, and so on.
My brother, the Golden Child, grew up to be a selfish piece of crap who cares for no one but himself. He expects everyone to give him money and gifts, but never reciprocates or even says thank you. He was raised wanting for nothing, and carried that into adulthood. He also married an N, who has verbally attacked both me and my sister, and he does nothing. He allows her to treat people like dirt, and just accepts it, much like my co-dependent father accepted my mother's behavior.
Which leaves my sister, who is the one in the middle. She's basically a vegetable. She saw NM abusing me, so became totally compliant. She does whatever she is told. She lives two doors down from them, works the career of M's choosing (which she is miserable in), and at 49, has never even dated. NM teases her about everything, so she just lives in her own tragic, isolated world. She's neither saint or hit-man. Just a puppet.
So I guess the theory is somewhat accurate, as my brother and I are polar opposites. I believe my sister got caught "in between" because she was never allowed to have autonomous thoughts, and never really developed into an adult.
