Marriage is over rated.
How do you know if you're really with your soul mate? People get married at some point when they grow tired of being single and looking for a mate. Then once you're married, the search for your soul mate ends. You're off the market for 5, 10, 20, 30 years at a time. Maybe you get lucky and you live happily ever after with your 1st choice as a mate. Who we choose to marry is based mainly on timing, fate, and the fact that the person you choose is what you feel is the best you could do at the time.
But how do you know, maybe your perfect mate is a happily married woman with 3 kids who lives across town. But you never met her because she's been off the market and married to some dufus for the last 20 years.