The whole incest thing is a curious one, if you had twins separated at birth that then met each other later & had no knowledge of their sibling status & fucked should they then later feel disgusted & break it off? It didn't become bad until they learned that truth but there was no issue beforehand.
A guy gets with some gross shit genes landwhale but that's acceptable due to no family connection?
Honestly what a crock of shit, as long as they're not having kids I see no issue, it's a pov that is socially conditioned into our heads by others before us, it's not disgusting of it's own accord, we're told to think that & so we do.
It can be argued that it's one thing to have sex with a parent but an aunt, niece, sister or cousin is something else; just don't be having kids & there's no retardation repercussions & other than that who the fuck cares & why is it an issue?