>>280509958
Not that it matters, as I said, but just going by definitions, most exclude their case. Some dictionaries specify it as sex between blood relatives, others as between people who are not legally allowed to marry. We don't know the latter with certainty, but as I said I doubt there was any documentation, and even if there was, we don't know if it's illegal in Paradis or whatever. So we're going by "they refer to each other as family but still wanna fuck so it's incest". Well, sure, why not...
Incest isn't illegal in my country, and reactions towards it aren't as strong. People still don't want to fuck their siblings, naturally, but you can already see a cultural difference when someone is inclined to view something as disgusting, even though it's pretty far from what the cultural norms even existed to prevent to begin with.