Most Helpful Guy
You have to be clear on what you mean by soulmates.
Are people born for each other, and destined to be together from the moment they set eyes on each other? Probably not.
We have this picture in our heads of our perfect prince-charming fantasy, but it never happens like we dream it too.
In the movies, they say things like "you are my destiny" (or in George McFly's case, "you are my density"), but in the movies they talk about following your destiny, and choosing to follow their destiny (which is contradictory because one cannot choose something that is pre-destined to happen), but most people believe in some form of free will.
The way I see it, our lives are a mixture if variables we can't control and ones we can. There might be a girl in Okinawa that is perfect for me, but living in America I will probably never meet her and that's just too bad.
And, another important point, is that people change over time. I'm not the same person I was 5 years ago, and 5 years from now I will likely be a different person. Nobody starts out perfect; we are unlikely to find someone who is automatically the person of our dreams.
A couple grows into each other as long as they spend time together. They change and they change each other.
All of that being said, I don't think people are born soulmates, I think that people BECOME soulmates.