Here is a copy and paste of someones comment exlainin it all
She is not from that world. She is not related to him by blood and you may think that they " well but their parents were were married " for siblings that are not related by blood to be considered "siblings" they have to have an EMOTIONAL connection, which they dont, because they literally met once( not sure) they are strangers to each other. Thought im not hoping for the story to take that turn, honestly it wouldn't surprise me. So i would love for you all to shill in the comments. Of you are the kind of person that gets offended or dislikes those types of plots( the ones that seem to be going towards" incest") you should problably stop reading when you feel that it makes you uncomfortable. It will save you some peace in mind.
I hope this doesn't become incest