an example. they are in a marriage or alike for several years
he - LII, she - EIE
he mistakes in own type as LSI, so thinks them as duals. this points, he likes the relations enough to suppose they can't be better
Semiduality is a complementation for most important - base function. While 2nd is strong and has different valued variant what can annoy, but not critically. The more problem is a lack of support for one of weak functions.
When it's both S types - they make comfortable and physically not bad place to live, but may miss opportunities for better life for them and people near them, have more doubts in a future, make more mistakes with understanding of situations and people. S types a little of "dumbs"
where they deal with not evident and not well-known.
When it's both N types - they may have interesting ideas and good plans which will never be realised on practice good enough to have a good use from them, may miss physical practicality and have worse living conditions in physical sense (for example, to get more problems with health than could).
Where S types look too much on the ground, N types look too much on the sky - what makes the ways of both more risky and having more problems. The duality reduces this accentuation for all weak functional regions.
My parrents were semiduals, mother's sister was with a semidual, grandfather and grandmother by father side could be too. I saw this IR pairs. Not bad ones, tend to be stable. With an activation IR I think them as acceptable for marriages, if you want to be good friends there.
2 of 3 cases of my significant feelings were to semiduals. Though, relations were accidentally broken in beginning stage much by external reasons and by my bad F to deal with people (redundant anger, for example).
In case a pair is formed with serious intentions, even when such people break - they should notice that keep much of attraction to each other and that to find a comparable one is not easy. So pairs should be stable (incl. when problems appear) and with a tendency to restore relations if those were broken (if other stable pair was not found).