Board Thread:Wiki/@comment-30049797-20160924003216/@comment-1327106-20170825231454

That's fine. Some fans don't consider anything canon unless it appears in the manga itself, even if it's something Isayama said in an interview. So if you want to call yourself one of those people that's your perogative.

But as far as the guidebook text is concerned, "adopted" looks like a valid translation, so you wouldn't be able to support your point of view with it.