! ! ! ! ! so it's kind of an unofficial MKR fandom tradition to ship Kuu with Geo but I was skimming the beginning of the MKR2 anime today and I realized she'd get along really well with Kakeru and Satoru! not necessarily to ship them or anything, just declare themselves the big siblings for all the Knights (since Umi is an only child)
I think she'd get along with Masaru too, the eldest? did I mess up Masaru vs Satoru, I forget, and am too lazy to spend very long googling it, why is it hard to find a birth order??? because Kuu can be plenty mature/serious but also has a goofy side. I think she'd be able to get along well with all the Shidou kids. <33
Satoru is definitely the oldest. I don't think there's ever been any
official statement about Maseru and Kakeru's ages, but based on the clothing each is wearing at the beginning of MKR2, as well as general appearance and height, I'd say that Maseru is the middle brother and Kakeru is the youngest brother. (At the beginning of MKR2, Maseru is wearing casual clothes and Kakeru is wearing what is very clearly a school uniform; Kakeru's face has a youthfulness shared by Kamui from
X, while Masaru's face looks rather like it is transitioning from looking like Kakeru's to looking like Satoru's; at the end of MKR2, Maseru is shown to be about half a head taller than Kakeru.)
Also, within the last year or so, I've come to realize that I actually do ship Satoru and Kuu with each other.