A divine complement is someone who shows you the exact mirror of where you are living. This person could be anyone at any given time the higher self sends to mirror your exact image. Often times it reflects our negative vibrations, while other times you are blessed with seeing the beauty that is you. A complement could come in and out of one's life, or stay around for a while completing many lessons for both parties involved. This would be a very good reason why marriages on earth shift all the time.
People change with age and move on.
Remember relationships on earth are in preparation for moving you to a higher level of being. A soul mate is one who is previously set up before coming into incarnation. Your cycle of life will take many turns and at the perfect time a soul mate will enter to teach you in a strong way about yourself. Many would like to think they are married with a soul mate, but truly not as many as would like to be are living this relationship. It is a special meeting and one that will most likely alter your life.