When do you become an Aunty/Uncle?

I know, I can hear you now – when your sister/brother has a baby, thank you very much, moving on to the next blog….. if only it was that simple.
I am an aunty to two (soon to be three – hence the reason for this thought process now) of two lovely little girls. Whenever they greet me or talk about me I am aunty, the problem is I am not. They are my cousins kids (my cousin doesn’t have any siblings, and we grew up around the corner from each other and he is more of a brother than a cousin.) When he and his fiancé had their first girl, we were still very close and although my cousin’s partner’s family (keeping up?) complained that we shouldn’t be given the title of aunts we were and life was good.
Enter baby number two, and although we don’t see as much of them as we did things are still good, we are all getting on, and there has been a very enjoyable nights bonding with the cousins fiancé including turning up to watch a film early, popping into the pub for a quick drink and having such a good time we missed the film, and I am an aunty again.
However since baby number two and soon to be baby number three there has been some misunderstanding which lead to small fallings out and then to a public slagging off on facebook (Why??) we aren’t as close a family as we used to be.
As well as these small arguments, there has been some massive changes in my life in between baby two and three, namely I have moved in with OH which gets me thinking at which point does he/does he ever become an Uncle? When I first receive the text to tell me the fiancé was in labour, I didn’t grab my phone to tell him, in fact I didn’t tell him until I realised that my sister has told her boyfriend (obviously I would have told him when I saw him tonight!) as I thought would he care? Then this got me on the whole thought process of well they are his family now to, hopefully we will be together forever and so he should look on them as family, does this mean he should become an Uncle. Or do you only become an Uncle when married, that was my sisters point when I discussed this with her. OH has told his nephews they can call me Aunty (which resulted in a question from them of, why are you getting married? Silence from the rest of the family and a quick diversion of conversation by OH)
His best friends kids have started to call me aunty (well in a card, I have only met them twice so…) at what point do I get my nieces to do the same? Is it even up to me?
I am sure it wasn’t like this in fairy tales! Whatever happened to boy meets girl, they fall in love and ride off into the sunset on a white horse!
Any ideas??
(And a complete side not should it be fiancée for a female rather than fiancé? I have just had this thought now oops!)