Was thinking about this after looking on the "partner" thread!
I've begun to call my boyfriend my "partner" recently, as the nurses in my hospital (I'm hospitalised a lot!) often try to refuse my BF as next of kin. We've been living together 6+ years (longer than some marriages one kindly nurse remarked!)
However one actually told me off for being stubborn when I refused to give any other name
Even though I haven't lived with my parents for years and they live a good hour away 
NHS website says "There is therefore no reason that your partner shouldn’t be treated as your ‘next of kin’ despite the fact that you are not married."
Why should the word fiance make any difference? Should I just refer to him as this?
Ps. apologies for the slightly rambling thread, it has been bothering me though!