My dad is ILE and he has pretty much always let me do what I want, only giving advice and teaching things such as computer programming, mathematics, languages and science. Occasionally practical things, but I surpassed him in those skills in my 20s already. His own parents were LIE and ESI who were strict in parenting style, so he decided that he would be relaxed with his own children. He has remarked sometimes how I remind him of his own father, triggered by Se/Ni traits I think, he doesn't really understand the point of them but can see the differences.
Both me and dad being Fi polr our conversations about relationships have always been awkward and few, but he has never in my life judged me for whatever I have done, only trying to understand it in a Ti way and sometimes offering some advice based on his own experiences. These days our discussions are mostly joking in nature, him often making jokes which are hit and miss for me depending on how much they're Ne or Ti based.
Mom is SEI and my siblings are also both Si/Ne valuing, which always made me stood out as a "black sheep" compared to the rest of the family, some exes (the Si/Ne valuing ones) even half-jokingly asking if I was adopted or what's up with me being so different from my family. I always thought they were too soft, too democratic, too non-competitive and non-confrontational, lacking ambition and focusing on "uncool" things.
And yeah, both my parents and grandparents truly are/were duals. My parents have been happily married for over 40 years (grandparents were also their whole life from the 20s), so my view of a normal marriage from home was duality which I think badly prepared me for the reality of non-duality romantic relationships and communication issues that can arise in them.
Sometimes you don't have motivation because you lack purpose.
Sometimes you don't have purpose, because you lack self-knowledge
Sometimes you don't have self-knowledge because you lack love
Sometimes you don't have love because you lack self-love
Sometimes you don't have self-love because you lack guess what? Ask Gulenko!!
I think their relationship is very natural and resilent. Of course, they fight sometimes, but it never escalates beyond a certain point and quickly bounces back. My mom (not very seriously) complains about my dad being childish and nerdy but at the same time loves his intellect and resourcefulness. Dad jokes about mom being dumb, unintellectual and jumping to incorrect conclusions but at the same time probably loves it.
Before socionics, I didn't even realize that this was not a common case with romantic relationships, and that communication issues don't automatically resolve themselves like they do in duality. And that only in positive ITRs your strengths do not hurt the weaknesses of the other party and vice versa.
Compared to many other relationships I know and have myself experienced, yes, duality is very good.