I have noticed that there is a pattern in the socionics intertype relationships between siblings.
There are many duals...but I think the most abundant relation is super ego. It makes sense, one of the kids is intuitive, the other a sensor ( - for instance); one of the kids uses logic , the other, ethics ( - for instance.) . This guarantees that one of the kids will thrive in the environment. My sis is SEE and , in Spain, gamma values are "popular": I am too nerdy perhaps. Had we been born in Japan,US, etc, I would be much more "popular" than her.
Dual kids is a "double or nothing" bet. Either both kids succeed or both fail. My cousins are alpha and they are "outcasts". I have other cousins who are both gammas and both are "successful"