sorry, but i need some perspective from people who know what i'm talking about, so please bear with me on this.
I've read the 'Daughters of' website inside out and upside down, and convinced my mother is narcisistic (sp?), or most def. has narc tendencies.
I am the eldest child, her 'golden child' also has terrible mental health issues. (just had a 6mth spell in hos, sectioned at least 10 times in the past 12 years
)
Before my sister met her DH, we were very close.
She stayed at my place, she ate with us, she babysat by way of 'payment' on occassions (this was her terminology, not mine), she moved into her own flat and became increasingly ill (i am NOT insinuating this was linked to her moving out, i'm not possessive of her) - this was her 1st section - and she turned against our mother.
She hated her with a real venom I've never seen her express before! Sis made ME her next of kin, alongside our father. This was fine/accepted in the family as we all felt it was the illness doing this, it wasn't 'personal' IYGWIM.
As she recovered, they got close again (back to golden child/narc mother) and sis met than man who is now her DH.
As sis developed her relationship with this man, I withdrew a little, no-one wants their big sis hanging about on dates do they 
Then things got a bit messy when DSIS announced her pregancy. Another sibling had a huge argument with DSIS's DP over the phone, but since this happened on MY phone, i got dragged in..blah blah blah. all sorts of shit was said, and, as is often the case, the blame landed with me - being the eldest/my phone/ etc. anyway, you get the drift i hope.