Has anybody ever had the golden child help address the situation?

Has anyone ever experienced the golden child come to the aid of the scapegoat rather than take the easy way out and try to appease the narcissistic parent?

For context, my MIL is a narcissist who primarily scape-goated my now deceased FIL. After he died 10 years ago, my wife and her brother took over trying to address her insatiable needs. I am very involved as well. I established poor boundaries because of how little I understood about narcissistic behavior at the time.

My wife is now the scapegoat and my BIL is the golden child. I thought he was smart enough to see what was going on. I have generally not complained to him when I’ve had conflict with my MIL. I knew he’d be bombarded by her anyway for sympathy. Because I am going so far above and beyond what any child should do, let along a son-in-law, I assumed he’d recognize that and be appreciative.

I’ve come to realize that I was incorrect about that. He has said that he doesn’t understand why my wife and I can’t just try a little harder to get along with her. Adding that if you just give a little she is not that unreasonable. But this is only true for him because he is the golden child. The rest of us get scapegoated.

It is worsening now to the point where he seems to actually believe the absurd stories of victimization that my MIL is telling him. It is very disturbing to us. My wife has finally become convinced to lessen contact. As a result, my MIL isn’t getting the conflict she craves from my wife and so she is meddling more in my BIL’s life. He has reached out to my wife for support, but are staying out of it.