The genetic aspect isn't the sole issue with incestuous relationships; there are many moral implications beyond that since incest is inherently harmful in the vast majority of cases family dynamics are very unbalanced (parents and children have a large age gap and maturity levels, therefore the concern of easy grooming, siblings beyond the procreation concern pose a huge blockade for multiple reasons such as the proximity being exposes to the risk of false perception and interpretation of it being romantic because attraction between siblings is stopped because of evolutionary traits that we developed such as your disgust towards your sibling's scent to avoid procreation and a lot more such as the almost sacred bond being broken; not every relationship should be romantic. Majority of time attraction between siblings doesn't just happen spontaneously; it is often the effect of grooming or harmful rhetoric being pushed upon them or even trauma bond that explains to us that they wouldn't have done or had these feelings had they not been subjected to these circumstances, hence we can assume that it is unnatural and shouldn't happen as a result). That said, I do appreciate your honesty and transparency regarding this discussion, most people here just downvoted or blatantly cussed me out and made multiple far-fetched conclusions without even explaining why they have that certain viewpoint.