I distinctly remember posting this 'somewhere', but I'm fairly sure it's not my blog.
I have never been the jealous type, and have always experienced strong feelings of compersion. Being also often somewhat unavailable time- or energy-wise (I have a busy family life), I played around with the idea of my partners having other girlfriends too that would be available when I wasn't. When I brought it up however, the response I got was 'But I only want to be with you'. So I thought this was just a peculiar quirk of mine and that people in general were not interested in multiple partners (at that point, I had never heard of NRE).
I've always had a very practical attitude to romantic relationships in the sense that I feel wary of the whole commitment issue while things are new and I'm still in-love. I usually feel better committing to friends and family than to lovers, because I've always had a very strong idea that romantic relationships are transitory. I did wonder where all the drama came from with the cheating and 'we are no longer in-love, now I'm in love with someone else' and people having to break up their families because they no longer were feeling the same way about their partners. When I brought this up with other people the responses I got were something along the lines of 'That's a cool idea, but there's no working around jealousy' or 'If relationships between two people are complicated, imagine adding a third - that's just too much hassle'.
Now when I read Deborah Anapol's book 'Polyamory' I immediately recognized that this was what I had always been talking about. I imagine having already read a lot of critiques of the traditional heterosexual nuclear family and marriage helped. Also, I saw polyamory as a way to live out my bisexuality. At that point, I did imagine being partnered with an established male-female or lesbian couple. What I've discovered so far is that 1) the less expectations, the better end result; 2) weird stuff happens and 3) my bisexuality is somewhat incidental.
So, I personally have never had problems with sexual fidelity and that was not my introduction to poly (I was single until very recently). It is more of a philosophical choice and yes, a LIFESTYLE
that resonates with who I feel I am inside.