So what? I honestly don't get the issue. It's pretend.
When sex is taboo our brains will often associate the two things and we end up enjoying the taboo-ness. Incest is a big taboo, so it's sex with extra taboo slathered on it. People will want to fantasize about it. It's how brains work. As long as it's in the realm of fantasy I don't think there's ANY issue.
I'll go further and say that if two consenting adult sibling want to have sex it shouldn't be anyone's business but their own. It's not the state's job to decide that they aren't allowed because it makes the rest of us uncomfortable.
When sex is taboo our brains will often associate the two things and we end up enjoying the taboo-ness. Incest is a big taboo, so it's sex with extra taboo slathered on it. People will want to fantasize about it. It's how brains work. As long as it's in the realm of fantasy I don't think there's ANY issue.
I'll go further and say that if two consenting adult sibling want to have sex it shouldn't be anyone's business but their own. It's not the state's job to decide that they aren't allowed because it makes the rest of us uncomfortable.