Different from the view most lovestruck people tend to take on this matter, to me there are many soul mates.
Taking my idea from the oldest roots, I believe one must look to the sacred balance of the masculine and feminine counterparts. Yin and Yang if you will. Together they complete each other, forming a circle, the simplest shape. This circle, love, is formed from the union of souls. A single soul is incomplete by itself, and therefore needs a soul mate. The result of not having this soul mate often ends up being unrequited love. So is that it then, just find someone who completes you?
In addition to completion, soul mates also serve another purpose. While searching for that "right one," it is impossible to not encounter other people along the way. Undoubtedly, a few of these people will have a profound and lasting effect on the personality and character that you possess. This is where the idea that there are multiple soul mates becomes evident to me.
Visualize, if you will, the Chinese Tai Chi symbol. Though its creation came from measurement of the Sun and Moon, its meaning also goes beyond simple heavenly bodies.
While the two sides of the Yin Yang obviously represent man and woman, one must question the origin of the shapes of each side. The Chinese derivation is found in the changes in the sky throughout the seasons. Could these changes not also be found within each person? While there is one soul mate for marriage and procreation, there must also be others that define each individual so that in this union, completion can be found.
Take each person as a puzzle piece. While there is only and can only be one other that fits correctly and completely with another, something must exist that shapes the individual uniquely. This is the other type of soul mate. There can be many of this kind. Each one reaches a different part of you and changes it ever so slightly. In terms of the Yin Yang, the image seen is an example of two of the simplest sides, Sun and Moon. While these are evenly and inversely matched, it must be taken into account that no two people are the same. Therefore, if you were to draw yourself as a Yin or a Yang, the boundaries would be different, and also the size.
By far, the soul matched to you, is the most important, but without the other souls affecting our personality and character, we could easily be completed by any random person.
Personally, I think that would dilute warmth and contentment found in returned love.