I suspect this is orders of magnitude more common than kids graduating university at 9. For instance everyone in my extended family speaks 3 languages at least

I suspect this is orders of magnitude more common than kids graduating university at 9. For instance everyone in my extended family speaks 3 languages at least, some 4, due to historical circumstances. It's simply a question of exposure. If you go to Fribourg in Switzerland there's a whole area where people speak both French, Swiss German, and High German. And these days English as well. The rest of the Swiss at least learn several languages in school, though perhaps not using them constantly.