Uhm... you people are weird, it's not wrong at all to love a brother/sister not like a brother/sister? Or to have sex between themseves regardless?
I can agree it's not fundamentally evil but it can't be labeled as correct in any Universe, as long as there's any good sense in it.
Word is that it's too much sex in these days everywhere
... but between siblings!? And think it's ok!??!? Now we know
I heard in news about half a decade ago a true story about a brother, rather undeveloped both intellectually as culture-wise, that has raped his own sister. When the news team interviewed the newly alleged rapist of kin, and asked him "Why did you do it?" he said "I saw my sister there (unconscious) and with her legs spread and I just got horny." As rape we can all agree is universally bad (and here I am on topic), raping your own kin breaths a whole new level of human decadence. Your kin is always susceptible and rather vulnerable to your suggestions and deeds as they are at home, a place supposedly safe and sane. Where do you really draw the line between consensual sex, vulnerability stages that can decline into all sorts of manipulation and ultimately pain old rape!? If you would be a parent, would you really be ok if your children would have sex with each other, regardless of their age? I don't think there is a parent in this world who would, even the morally and mentally undeveloped ones in undeveloped countries in Africa or SE Asia, except if it's an extremely deranged family, as a total exception to its undeveloped society.
I am an only child, maybe I am in the dark regarding this subject, but then ask brothers and sisters if they would ever screw under normal circumstances, and if it would be ok even under abnormal circumstances. If you get even 1% positive feed back, I will agree I am wrong, and not all forms of incest are undecent. 1% is not a lot, probably the crazy percentage out there is higher! So even the crazy won't go for it in my opinion.