Too bad. You're missing out. Again, it's no ACTUAL incest. He just took in the girl and TREATS her like a sister. This is the equivalent of getting upset over a childhood friend.
If this was real incest then I'd understand but avoiding anything that only vaguely looks like incest is just ridiculous. It's either incest or it's not. If it's not, don't treat it like it is.
This isn't a high horse situation. You're just making it look worse than it is in your mind. You say you understand but do you really? Last time I checked, you are the one that tried to make it seem almost as bad, if not as bad as actual incest.
In fact, you have yet to explain WHY you are so against it in the first place despite knowing that the incest isn't real.

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