Nonsense, weegiemum, that is my role. 
Realizing that a relationship is unsalvageable is an epiphany moment isn't it? I am nearly there with my narcissistic middle sister.
Both my parents are deceased. I was never close to my mother, bonded with dad but there were restrictions (he was deaf). I finally realized that I never bonded with mother, nor she with me, even as an infant. She followed "Dr. Spock"-let them cry it out-so if I ever cried, I cried alone. I was treated as an invisible child.
I think I cried 5 min. the day she died (I was 18) and that was because Dad was crying. That was it; I just didn't/couldn't feel anything. I was completely numb and that went on for decades.
Sorry to ramble on, but I can see that if mother had lived that the extra time with her wouldn't have been for anything good for me. And I can sense that I would have had to come to the conclusion to set major boundaries as so many brave and intelligent women here have done and are considering doing.
It can be done. It is not something frivilous or light, and can be very emotionally painful. BUT...the relief and the hope for personal healing, the actual personal healing and the emancipation of your soul are the glorious rewards for having the courage to stand up for yourself, to mean it, and to not backdown.
Weegiemum, the people that won't let you move on have you enmeshed in a family role. It is like an anchor sinking you in the past forever. I don't think they will change, or suddenly acknowledge that you are an evolved human being-adult, intelligent, respectable, lovable. Cut those anchors loose. You will thrive. It is your life-and 40 is not old at all. (I'm 48-that's old.
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