THANK GOD I DIDN'T READ THE INCEST TAG.
The story seems wholesome despite the sort of problematic nature of it... But being fair, with how things are going I highly doubt THAT man child is going to be making a move on her, and like a few other comments have said, it's not like this sort of practice was uncommon: Sometimes even a 5 year old would be engaged to a 15 year old. It was all politics and nothing else, everyone recognised it as such so it wasn't seen in a negative light and couples like that didn't officially marry until both parties were older.