Ceros:
Let's say, I like that anime stereotype too
I've also heard an opinion, that only people who never had any siblings can imagine (wish) such relationships. I bet you don't have any
Me too.
In general, I don't see any problem if both people agree about it. (I recall one scene from anime, where two cousins (boy and girl) "help" each other to satisfy their "needs" while not having any non-incest sex partners.)
But I don't want to say "it's a good thing". Only because when I become famous, that crazy celebrity hunters would quote me ("He advocates incest!!!" Imagine newspaper headings here, lol).