I read an article some time ago that said that children pick up languages easily and naturally (almost by osmosis, as it were) up until age 12–14 or so. Then, somehow, a switch goes off in the brain, and it becomes a lot harder to learn a new language. It’s possible, of course, but a lot harder. I don’t remember the publication in which the article appeared, but you could probably Google it. Maybe something like that has happened to that individual, only to a much greater degree.