I absolutely believe in soulmates, but I don't think we are limited to just one. And I don't think the relationship has to be physically intimate in order for the people to be soulmates. I consider my best girlfriend every bit as much my soulmate as I do my husband. She instinctively knows what I'm thinking and vice versa. This is not something that we've acquired over the years, but was inate to our relationship and something we've shared from the beginning. I also think there are soulmates out there we don't even know....even though I'm happily married, I used to work with a man who I felt was my soulmate. We had a very strong connection, and even though the relationship would never become intimate (either physically or emotionally), I did feel that if our situations were different he could very well be the one.
As far as becoming soulmates, I think people who are destined for a connection can hone the relationship and make it better, but I don't think you can hone that relationship with someone who is not your soulmate. Does that make sense? You either have the connection or you don't.