We need a new word.

[KansDem]

10. Soulmate

A soulmate (or soul mate) is believed by some to be the person with whom one has a feeling of deep or natural affinity, similarity, love, sex, intimacy, sexuality, spirituality, or compatibility.

I know it can be overused, but consider the history of the term:

Plato
In his dialogue The Symposium, Plato has Aristophanes present a story about soul mates. Aristophanes states that humans originally had four arms, four legs, and a single head made of two faces, but Zeus feared their power and split them all in half, condemning them to spend their lives searching for the other half to complete them.[1]

It certain describes your comment, In fact, it's wonderful that they found each other

Also...

Theosophy
According to Theosophy, whose claims were modified by Edgar Cayce, God created androgynous souls—equally male and female. Later theories postulate that the souls split into separate genders, perhaps because they incurred karma while playing around on the Earth, or "separation from God." Over a number of reincarnations, each half seeks the other. When all karmic debt is purged, the two will fuse back together and return to the ultimate.[2][3]

--more--
http://en.wikipedia.org/wiki/Soulmate

I found my "soulmate" decades ago...