I was thinking moreso:
Osomatsu - ENTP (7w8...8w7...3w2...; sx/sp)
Karamatsu - ESFJ (9w1...2w3...7w6...; sx/so)
Choromatsu - INFJ (1w9...5w4...3w4...; so/sx)
Ichimatsu - ISTP (6w5...4w5...8w9...; sp/sx)
Jyushimatsu - ENFP (Jyushi is such a wildcard that I don't even know)
Todomatsu - ESFP (1w2...8w7...3w2; so/sp)
Osomatsu is full of ideas and is not afraid at all to break and test social norms to express these. His Ti is definitely more visible in
Osomatsu-kun. Even though that adaptation focused less on the sextuplets and more on Iyami and Chibita, the fact that the Matsunos, Oso in particular, are clever and mischievous. He may appear to be unaffected by most things, Oso cares deeply about his family. His auxiliary Fe shows when he assumes the role of leader in almost every situation. In episode 24, when that fairly well developed Fe is put to the test, it also gives us insight on Oso's inferior Si affects him in very typical ways like not wanting to move on from things, clinging to ideals that are no longer obtainable, etc.
Despite
Karamatsu narcissism and wacky sense of fashion, I don't think he has introverted feeling. I think he is Fe dom. At the end of the day, he just wants his brothers to notice him and is very willing to do what it takes to win their approval
as long as he is feeling up to it, that is. Inferior Ti sure can demotivate you at times... Though his auxiliary Si is very much warped in some way, it still makes it possible for him to make meaningful gestures towards those around him from what he has been given to work with. Kara is treated poorly constantly yet he is very forgiving. I think that tertiary Ne contributes to that, as he quick to make conclusions that lead to more hopeful results.
Choromatsu as a character is written to be "the guy who is supposed to look like the voice of reason, but he's just as bad as everyone else". His Ni and the future he has been planning/working towards seems to constantly conflict with his auxiliary Fe and its want to please both his NEET brothers and the society he assumes to think that he is utterly incompetent because of said comfort in NEEThood. His idol obsession may manifest from tertiary Ti and its habit to latch onto topics it finds worthy and going a long way with it. Inferior Se makes him very awkward and uncoordinated. Compared to his brothers, Choro is always the one caught off guard by the crazy antic of the day.
Ichimatsu is reserved and actually pretty fucking sensitive. He isn't able to communicate that, however, and is practically unreadable emotion wise. Most episodes that focus on him explore his inferior Fe, but his Ti gets showcased here and there as well. Ichimatsu has amazing deduction skills and while he isn't exactly studious like his older brother Choro, he is often implied to be very smart and knowledged in really less conventional stuff. Se is especially apparent when he is caring for his cats and interacting with his younger brother.
Speaking of which,
Jyushimatsu, like his eldest brother Oso, is bursting at the seams with concepts and is extremely friendly. Despite what one would initially think when looking at Jyushimatsu, he is actually very introspective as he constantly questions his existence, his emotions, and why he does the things he do (though most of his brothers are a little off put by such deep thought). He is also a real go getter and when he is set on something, he could easily move mountains to get it. And as inferior Si usually plays out, he is very disorganized and clumsy,
Todomatsu, while perhaps appearing like a stereotypical ESFJ, actually has a strong Fi. Being the youngest of sextuplets, individuality is a big concern of Totty's. His attitude of "don't tell me what to do, I can do it myself" is probably his Te not wanting anyone to interfere as he pushes forward with Se. After all, it takes some strong Se to be so in tune with the world and how to navigate within it. He's social and engaging. The only problem is that he tends to not set a solid goal for himself, he'd rather thrive in the current moment than sit around worrying about what's next.
At least, those are my justifications. Oso as an ESTP is a very valid argument, as well as Ichi as an INTP. Didn't mean to actually go that far when thinking about this.

I just really,
really like this anime.
And just for shits and giggles:
Iyami - INTJ (6w7; so/sp)
Chibita - ISTJ (2w3; sx/sp)
Totoko - ESTx (3w4; sp/so)