I totally believe in soulmates, but I don't believe that there is only one for everyone. I believe a soulmate is just a person who makes you so unbelievable happy when you are with them. So, a best friend can be a soulmate in a completely platonic way. So maybe when two people are together and feel 'love' or whatever their souls are physically meeting, or maybe the soul can be described as the chemistry in a person's body and the 'meeting' is just pure human bondage.
It's one of those things...