So basically idk...i don't like kota anymore? Ik he's like dating himself but...that's technically also his brother...AND HIS DAD...so...yeah...more context please?
i remember from watching noragami, that gods could do bad things but if humans were to do the exact same thing, the guilt would cause some kind of corruption or something like that. i thought it's an interesting perspective, that gods don't need to abide to the rules and they are not wrong if they don't. but gods require the worship of humans to be able to exist and have power. of course, this is all made up lore, but still an entertaining perspective to look at divinity and morality as a concept.
I'll admit, I was always confused on the whole 'brother' thing, cause the way he described their birth sounded more accord to the concept of 'soulmates'. But if I remember right, that might be a more western concept and in the east it might be more familiar? Will admit, not to shocked, cause look at literally any mythology, you can't really escape the insect whenever a god's family tree is inspected
Kota and Onsen aren't really brothers in a mortal/human sense. They're two beings created through the splitting of a river deity. There isn't really a, say, biological component to it. They're brothers in the sense they have the same progenitor. But they didn't share a womb or anything.
Lots of myth from virtually every culture works this way, or in even wilder ones. The nordic god Kvasir was born after a bunch of other gods chewed berries, spit into a cup, and mixed their spit together. Aphrodite spawned from the cut-off testicles of the titan Uranus, and that isn't even close to the strangest birth in Greek myth.
They're just... different. They aren't siblings in the same way we would be.