I'm a soulmate skeptic. I think of humans as boats or ships. We meet other boats and travel together. Sometimes shortly, sometimes a long time.
Some privileged, lucky people (I'm one of those) have the possibility to go out onto the high seas and look for other boats. Some people are stuck in shallow river and have virtually no chance to cross the paths of other boats.
You have to steer a boat. How you steer the boat of your life depends on what you experienced growing up. Maybe you go in tight circles and no other boats want to stay next to you. Maybe you go in straight line ramming other boats that get in your way.
If you're very lucky you learn to to steer better over time. You meet someone who went through similar experiences and steers mostly like you do. You can travel together for a really long time. But you have to want to steer towards the same goals if you want to stay together...and then you have to actually steer, not just drift.
If you don't discuss with your fellow captain where you want to go, and one or both of you has a lot of opportunities and/or obstacles, you can easily find your paths diverging.
Keeping your boats traveling the same direction doesn't happen by chance. Life isn't a fable. The gods aren't going to lash your boats together. You have to choose to steer the same way.
The more you have in common with your fellow captain, the easier it will be for you both to want to go the same way.
I got "lucky" the second/third time around after a horrendous shipwreck of a first marriage, then a near capsizing with my second wife. I'm also her second husband. We were born half a world apart, but have a LOT in common regarding how we want to live, what we find funny, and when/how/where to put up the mast (wink wink), among other things.
Our "luck" is a matter of our pasts, but also how we have both learned to steer and discuss where we want to go. It doesn't happen by some magic red-thread.