Agree. Incest. The summary mentioned incest tag already. So you guys who don't like incest (blood-related or not) should just go away. Your dream pairing would only stay a dream.
As someone who was adopted, it is disappointing. I like the story well enough to keep reading, but it definitely makes me uncomfortable probably on a different level from most people. Blood or not, I couldn't imagine dating anyone in my adoptive family. Even extended.