Bunny, you made great points, and I agree.
In my case, my 80-yr old NMom has always played her daughters against each other and still does. My Nmom was divorced from my dad since I was 9 (i'm 52). She robbed us of a relationship with him for many years.
I don't know who's manipulating who, but right now it appears, the 2 Nsisters are making sure they are taking care of my 80yr old Nmom's estate, will, etc. They didn't even talk to her a few years ago, and now they go on vacations together! Nmom doesn't see or even care if they are in it for selfish gain (estate) as long as they are giving her Nsupply. And it appears, the 2 Nsisters are in it for control of her "will" and estate, which believe me doesn't amount to much.
It's just they want to be IN CONTROL by leaving me (and my step sis) out of the picture. It started in May when my dad passed away this May, and made his oldest daughter the executor (even though she was biologically not his). My 2N sisters became the devil incarnate, and madeher position as executor MISERABLE, withholding documents they had, etc. and totally ignored any input I had, so I dropped out of the picture, sick of them.
Since then, they were DETERMINED to handle Nmom's affairs. The even convinced Nmom to move back to the area where the youngest Nsis lives and the 2 Nsisters are weaving their evil web. They continued to verbally, & emotionally abuse me and our oldest 'normal" sister the entire few months she was trying to settle his affairs. She could do NOTHING right in their eyes because they were so mad that dad made her executor. They said he should have never made her executor since she wasn't "blood".
So the oldest sister is FINALLY seeing how MEAN the 2N sisters and Nmom are because they finally were exposed when they got IN HER FACE. I was the only one who saw it for years, and no one believed me.
Since my Dad passed away My older "normal" sister, my brother in law, and her daughter have seen the light, and I have FINALLY been validated, and vindicated.
I think my Daddy was pulling strings in heaven for me!

Thanks Dad. . I miss you. He was the only one who ever validated or loved me in the family. I have a great husband of 18 years though, and many loving friends.
Thanks for listening, it's so nice to have a VOICE!