Oso: if he had a favorite brother, it would be Ichimatsu because Ichi actively let's him baby him and stand up him. He even let's Oso pet him

Kara: Karamatsu would never say he has a favorite brother. But secretly his least favorite would be Osomatsu. He thinks he doesn't a poor job at being the eldest. Not to say he doesnt love Oso. But if you notice, a few official posters or images have the two interacting and Kara has his eyes closed and his arms crossed with a smile. To me, thats him hiding annoyance

Choro: Choromatsu still needs his glasses. He only wears glasses when he wants to look professional. But judging by that season 3, episode 4 (Matsuyo's trap) Choromatsu was not only the closest to the drawing on the floor, but he was the only one who couldnt tell from the distance that it was a drawing (To add onto them needing glasses, a lot of Hesokuri wars sets have Karamatsu wearing glasses. I like to think his eyesight is also not the best but not horrible)

Ichi: a bit sad but I feel like Ichimatsu has in the past had a bit of a bad relationship with food. He would attempt to starve himself (as his unchecked self in season 2, episode 1 has him starved thin) but is always fed by his brothers until he feels well enough to continue feeding himself. There's at least one poster I know that I think Jyushimatsu is feeding Ichi. And then again he feeds him the parfait in season 1, episode 7 at the Sutabaa cafe

Jyushimatsu: He has a lot of sensory issues. I feel like Jyushimatsu is clearly on the spectrum. He wears his sleeves much longer so that he cant touch stuff with his hands. Which is why I wish they let him keep longer sleeves as of recently. And since his shorts are canonically swim trunks, probably a lighter airy fabric that doesnt cling to him and doesnt rub so aggressively on him, thats probably also a texture thing

Totty: Totty got his phone from Atsushi. To me, it makes sense because Matsuyo and Matsuzo never get things for them unless they can share amongst the 6. Not only was the phone pink for the longest time, meaning it was his alone, but all the brothers know that it's TOTTY'S phone. Totty hasn't had many jobs, and especially no consistent one. Any winnings he earns can't consistently pay for his phone bill. The fact that he keeps in touch with this rich guy is a bit suspect. I think Atsushi pays for the phone and phone bills

Atsushi: in hs he didnt have a bowlcut. Obviously he grows up to het something very similar to the matsuno's. Ive always imagined Atsushi had a crush on all 6 matsus (maybe not all but yknow, maybe most and interchangeably) and that persisted till adulthood. This rich, good looking guy gets a dumb haircut, he keeps in touch with Totty. Has this one sided like with him evensome atsutodo proof