Originally Posted by Emissary of Justice
Read what I wrote again: "...father AND uncle."
AMA was saying he thought Kaien was Isshin's son.
Ahem, let's me just remind you about how things work in Soul Society, since you either forgot or didn't know to begin with.
So there's nothing wrong about what I said. Family titles don't really mean anything in Soul Society. A tiny percentage of family members actually find each other while everybody else is pretty much adopted by each other. A person who just died can come there and wind up living in a "family" of completely random people he just met and over the years (and decades, and centuries, etc...) come to form family bonds with them like that.
So there's really no definite proof that anybody
in the Shiba clan is blood related to begin with. They could all be a big foster family for all we know, so Isshin being called "Uncle" is irrelevant. He could very well think of Kaien as a son, if that's the kind of relationship the two of them fostered. It's just a title that implies that he's older then Kaien, Ganjo, and Kukaku, and that they respect him as their elder no different then a real family might.
So yeah, no incest involved.