Some of my friends had a discussion about this... and it got me thinking... I'm not sure what my position on that is.
This sort of goes along with my thoughts on Fate, but rather than having to do with whether or not we really control our destiny, this is more about figuring out what our destiny is, if it is predetermined. Once we figure that out, we'll know if we have a soulmate.
I don't think I believe that everyone is put on the planet with one and only one exclusive soulmate. Rather, I believe that with all the people in the world, sheer numbers and probability convince me that there must be someone out there for everyone, possibly even more than one someone.
It's just a matter of finding that someone, which may or may not happen in one's lifetime.
It's sort of like the idea of there being other life in the universe. Numbers and probability say there MUST be, but there's very little chance of us finding it in my lifetime.