I know about Older Sister Syndrome. But have you ever heard of this happening?

[Grasswire2]

As adults, older sister turns siblings against mother so as to become the mother figure of the extended family, and shut mom out?

That has actually happened to me. I just figured it out.
She abducted my special needs adult daughter almost two years ago.
She has turned my sons against me, making up a weird narrative that puts her at the top of the family.
She's now talking about commiting my special needs daughter to a residential facility for people w disabilities.
She has NOT tried to obtain legal guardianship, by the way, of special needs dtr.

This seems to be an exacerbated Older Sister Syndrome type of thing where she acts to draw siblings to herself and shut out the mother. She has always been super bossy -- her siblings called her "Hitler" when they were young.

[JustAnotherGen]

1. My SIL

Rosanna started down that path and her siblings put and end to it very quickly.

[XanaDUer2]

2. Not heard of it

But sorry youre going thru this

[Grasswire2]

3. It is bizarre.

Over the last twenty years or so, she has turned her own children against their natural father (after which he drowned his sorrow in alcohol) as well as meddling in my relationships with grown children. There's something really wrong, emotionally and in terms of mental health.

[Mike 03]

4. This is something I've not heard of before

First, I am really sorry you're going through this. It sounds really depressing for any parent to have these types of social dynamics going on. I had younger twin sisters so it was a very different situation, which them competing with each other at first, then going off in completely different directions so they could not be compared to each other at all.

Does this syndrome coincide with any personality disorders?

I've definitely seen mothers turn their children against a father, especially one who is accused of some cultural wrongdoing, or in the case of divorce.

It's kind of a strange behavior from the survival point of view. Maybe the daughter is competing with the mother, but it seems like the benefit would be really small, maybe only mattering to shore up the ego? (That's why I wonder about a concomitant personality disorder).

Wow, I sure hope this calms down. Nearly all of the annoying, bad things we three kids did when we were younger resolved as we matured. From time to time, old patterns reemerge, though.

[Grasswire2]

5. interesting comment of yours

This same daughter did also turn her own young adult children (my grandchildren) against their father after their divorce. Bitterly did it. He turned to alcohol, with a ruined life and eventually died.

She also interfered when her brother, my oldest son, ended up losing custody of his daughters. She was part of the wrongful attack on him.

There's obviously a mental health issue. Something to do with power over other family members.

If there's any interesting data, it's that her siblings (a sister, two brothers) called her "Hitler" in their growing up years for her bossy ways.

[Grasswire2]

6. I have tried to identify what personality disorder would be most likely.

NPD (narcissism) seems too likely, and might just underlie something else. demonstrated by the willingness to hurt other family members in the grasp for power.

And think of this. She abducted my special needs daughter from our comfortable home (I have sheltered the SN dtr all of her 53 years) -- took her to her own home where SN dtr is currently living in the garage with the chickens. SN dtr had freedom here to take the bus to supermarket to shop by herself, she was safe in this very familiar and safe environment where she pursued hobbies and interests. Now she is constrained, and older sister intends to commit her to a residential facility for SN adults who are more disabled.

I went to Adult Protective Services when she was abducted, but they told me there was nothing they could do.