Well, see...my ex before that, whom I lived with for a couple of years, is one of my very best friends, so it's odd, I always thought that someone you shared a piece of your life with (and didn't fight too much with, which I haven't done with any of them) would mean something to you. But in this, as in so much else, it's the individual case that matters.

Also, I've never had any problems with their new partners before, so that is also new to my personal history.
I think this time it's because I didn't much like the woman before they became an item...oh well...