Good morning Mobius.
I will weigh in on a subject dear to my heart. I have been studying this very subject for a number of years. I might preface this with the premise that we can never really KNOW for sure any of this... so what we "learn" is really subjective. After reading countless books, years of meditation, consultation with other seekers and reading here on this forum, I've come to a few conclusions (very malleable conclusions!: angel) of my own. I believe we have many soul mates. I think we travel through our life times with these kindred souls for purposes of learning. Any given life time can involve any number of these fellow soul entities. BUT, and here comes my understanding of it, I believe we each have a Twin Soul.
Twin soul theory comes from many ancient creation concepts. I am not by any means an expert. But my understanding is that when the Great Creator (whatever you believe that to be) issued forth these souls into their human journey, He/She divided them from their perfection, and cast them into the world in search of each other. I know that sounds simplistic and their must be a lot more to it, but if I think of nature as a model, there is always a positive and a negative charge to everything. The ancient Yin-Yang teachings relate, in my opinion. As we progress through the ages searching for the perfection we once were, we do so in soul groups... the soul mates you refer to. Is our twin soul, the other half of our sacred entity there too? I think so... but again this is all intuition and faith.
There are many good books on this subject, and one I recommend is
Twin Souls: Finding Your True Spiritual Partner by Maurie Pressman MD and Patricia Joudry. This book offered the most sensible suppositions and hypothesis. They described the qualities and characteristics that they felt identified Twin Souls and went so far as to name Twin Soul couples in history. Part of their theory is that we seek this "other half" in order to learn. And when we encounter them it is not always destined to be beautiful, with showers of flower petals and harp music. No they say we will have very rough, very sad, and very complicated encounters... and once in a while we will spend a life of bliss. Twin Souls ignite each other when they come into contact. The passion is unmistakeable and powerful, and, according to Pressman and Joudry, this is a factor in the identification process. BUT, they go on to say that we will spend life times where we do not encounter our Twin. Why? Well, they say it is all part of the growing process.
There is much, much more to all this. And it is a deep journey in understanding it. I once had an indignant fellow tell me on this forum that this "Duality" idea was a cop out for individuals. From his vantage point it was, but then again that was his journey... something he needed to learn.
SO, in conclusion is our spouse our soul mate? In my opinion no, not always. The people we encounter, and have strong bonds to, could all be soul mates.(IMO

). I personally believe in the Twin Soul theory. I know mine is out there, I've met her and in this life we are a complicated jumble of emotions and relationships. But as I go deeper into this life time I realize the beauty in these challenges. As I witnessed my past lives with her in regression, I could see how we each are always teaching the other... even in the great sadness and tragedies. Sometimes the only salvation is stepping back and seeing the "big picture" of many lives, and knowing that some life time, some eventuality, will once again be perfect in a deep, sacred and eternal way.
Tinkerman