Responses
Think about it this way: they aren't brother and sister. They just treat each other as they are. In other words, don't think of it as incest at all because it's not. Although, it's pretty clear that he doesn't see his sister that way like she does him. So it doesn't matter.
I really like the concept of the power it makes for an interesting story. But the pseudo incest just kills it for me. I am not interested at all in that and probably won’t keep reading