I'm not sure exactly what you mean in your question, but I'm a Latter-day Saint (Mormon) and we believe in eternal marriage, which equates to having a soul mate for ever. The marriage is forever, not just till death.
It is also a common cultural belief amongst Mormons (I don't know how doctrinal this is) that many of us knew our husband/wife in the previous life. We follow inner guidance of the Holy Spirit when we get married... so it is possible that we marry someone with whom we had made a promise in the previous life.
When I was dating my husband, that song "I knew I loved you before I met you" rang so true for me. It still is. We have only been married for a little less than ten years but it feels like I have lived my whole life with him by my side... he's my brother, my sister, my mother, my father, my best friend.