Anyways as someone with many siblings I don’t understand how y’all romanticize incest so much. Yes I know it’s fictional. The only incest I’ll allow is step siblings that just met each other.
This particular story does not romanticize incest at all. On the contrary, it explicitly deals with how hard it is to feel attracted to a sibling. Because you cannot help who you feel attracted to. You can only control your actions.
Stories like these are super interesting (even some of the ones with actual incest, depending on how it's written). They allow us to get a different perspective about the world that we wouldn't have otherwise. It's the same reason why Nabokov wrote Lolita (although I haven't read that one so I can't tell if it's any good): to explore a difficult subject matter in a medium where it causes no harm to anyone.
Of course, that's considering the story doesn't actually romanticize these themes, in which case it may well cause harm (I will forever hate a few bdsm movies on Netflix for how much they romanticize abuse and other clear violations of consent). But it's not the case here.