Soulmate: compatibility or complementing

I have always been intrigued with the notion of finding one's soulmate. I had reflected upon this notion many years ago and had concluded (then) that, "soulmate is hard to identify instantaneously and most people do not meet theirs in their current lifetime." I had pondered on its definition: a person with whom one has a feeling of deep and natural affinity; similarity; love; intimacy; sexuality; spirituality; or compatibility. In a related (spiritual) concept: is that of the twin flame or twin soul, which is thought to be the ultimate soulmate.

Therefore, when two person (putting gender aside) have the capability of existing or performing in harmonious or congenial combination, does it mean that they have found their soulmate? Does this mean that one's soulmate can be one's sister, brother, female friend, male friend or anyone who has established a close and harmonious relationship with us? I think this is possible and I believe that one can have more than one soulmates in one's life; they appear at a certain phase of our life to bring balance and harmony into our life.