I have friends in a similar situation: living in France and both speaking a perfect French, but the father is a native German speaker. His main technique, durin

I have friends in a similar situation: living in France and both speaking a perfect French, but the father is a native German speaker. His main technique, during the first 3 years of his son, was to talk to him in French, but immediately repeat the same thing in German, and making clear that it was just the same thing in another language. Now his son is 8, and truly bilingual.