Quote Originally Posted by ThroneofDravaris
That’s no way near as bad as some shows I’ve heard about. In the anime OVA ‘Angelic Sanctuary’, the protagonist is in love with his sister (ie his blood related sister) and from what I've heard, he actually has 'relations' with her (lol, worst pun EVER).

How’s that for socially unacceptable!
Ah, but angels are genetically perfect, so there's no risk of recessive mutations coming to the fore. The same reason the Greek Gods were allowed to get fruity with their siblings.

Brother and Yuna are first cousins, so... it happens sometimes, and plenty of couples exist who're first cousins. It doesn't necessarily have adverse consequences for the kids. However, the closeness of the family relationship is a moral problem for some people. Some would say they're too closely related; others might disagree.