Is this a case study of what becomes of the Golden Child?

[Blueberry Pancakes]

When my golden child sister got married, the family knew her husband was moody, distant, and controlling but the we accepted him because he was my sister's choice.  A few years ago I was at their house while they had a huge argument about their dog, and saw the rage in my BIL's face and it was clear my golden child sibling had married a man who was way more than just difficult. My sister admitted he refuses to let her have an ATM card, she cannot have direct access to their bank accounts, he hires private investigators to follow her around when he is out of town, he constantly accuses her of having an affair (which she is not), and he tracks texts and her whereabouts on her phone. She also admitted he hits her on occasion, but only "after she hits him first to get away from him." She puts on a great show of normalcy. They flaunt their money with cars, boats and vacations. The only outward sign is that one of her fingers is bent from being broken one time when her husband pushed her to the ground. She has turned down my offers of help and does think the abuse is that bad.  I am NC with my sister now, but my parents recently mentioned that my sister asked them to remove her from their Will because if she inherits any money it will put her in a tax bracket where she and her husband will actually have to pay more. I was astonished. I do not know tax laws, but such a scenario seems unlikely to me. Also, it is none of my BIL's business what my parents do with their money and he seems to be out line imposing his demands.  It made me question if my BIL was threatened by my sister having her own money, so he convinced her to disinherit herself.  Then I wondered is this an example of how a golden child continues the pattern of letting themselves be manipulated by the one they seek approval from? It seems a cautionary tale if my sister has given up her entire identify for this guy.  Any thoughts, or has anyone experienced similar? Thanks. 

[Medowynd]

Your right that an inheritance would not affect their tax bracket.  Your parents should speak to an attorney about setting a trust or another vehicle that would prevent BIL from touching it.  Hopefully someday, your sister will decide to leave her abuser.  But who knows what kinds of threats he has made to her.

[qcdlvl]

I don't know if it's a common outcome, but it sounds a bit like a dysfunctional family I know (not mine, thankfully) - classic dysfunction in having a GC, a SG and a lost child. One parent is an alcoholic, the other one has fleas I think.
The GC is married to someone who is apparently a malignant narcissist. They row daily, and in her rages she at least sometimes slaps the GC. She has largely made him cut off his FOO. Ironically both the SG and the LC have seemingly good partners. Perhaps some GC become addicted to approval from someone dysfunctional?