Most of the people are lucky to have a Soul mate in their Life.
Concept of Soul mate generally starts with an Attractive conversation, then Crush, followed by Infatuation, then leads to Love, Understanding finally to Marriage -> perfect Parents -> Grandparents and so on.
Yeah, exceptional cases would by-pass few levels as well.
If one of the above relationship is not working properly, then remember that it might be definitely because of one of the 5 elements of Human Nature.
Ego, Complaints, Judgement, Expectation or Acceptance.
Read next
From @siris10