Normally, when you think of soulmates you think of a love that "transcends time." One love that transcends time. While I do think we have soulmates, I think we have many soulmates; when you have a lesson to learn, certain kinds of people are brought into your life, over and over again. If you fail with one, at some point another will enter, until you either learn that particular lesson or die whichever comes first. This probably comes from an idea in psychology that we are attracted to people who are similar to problematic parental figures - we are unconsciously drawn to people who have the same issues as a difficult parent because we're unconsciously trying to resolve our issues with that parent. I realize I've had several Hades that have passed through my life, and each one was an opportunity to learn the particular lessons that I've been struggling with the last few months. This idea is so much richer and more rewarding than the "one true love" fantasy promoted by our culture - there is no "one right person" for us. There are many right people, and each one presents us with an opportunity to live and grow.
The other thing people normally associate with the idea of soulmates is that it's a romantic relationship, which seems too limited to me. I think the term applies to any truly heart to heart relationship - romanctic love is just one kind of love. So many people pass in and out of our lives, and yet we connect with so very few. There's something almost magical about it when we make that special connection - there's definitely a sense of souls touching. And that's what I think a soulmate relationship really is when you boil it down to its essence.
As with so many things, people try to make soulmates out to be this fake, larger than life thing, when the real thing is more magical than its Hollywood imaginary shadow could ever be.