Socionics, which is a Jungian typology that's similar to but different from MBTI developed primarily in Russia, provides some of the evidence for this. The typ

Socionics, which is a Jungian typology that's similar to but different from MBTI developed primarily in Russia, provides some of the evidence for this. The types in Socionics don't map one-to-one onto MBTI types, but the general idea of what the grandparent is saying is supported by the concept of "dual" types within Socionics. The basic idea behind a duals is that you get along best with people who share your attitudes/proclivities, but have complementary strengths/weaknesses within those dispositions. And yes, meeting duals is often pretty hard, especially for certain pairs, because they move in different social circles and environments. It's very interesting stuff and it seems to me like it's onto something, but it's still pretty fringe, and has not been convincingly statistically validated yet. I'm very interested in formalizing these notions and subjecting them to statistically well-founded empirical tests. Right now there's a lot of enthusiasm for Socionics in Russia, but not much work in the Western world. Email or IM me if interested in chatting about this. Also, since it's so new, beware of crackpottery... there's some people who claim absurd things like being able to determine someone's dominant Socionic type just by seeing a photograph.