Can You Lose Your Native Tongue?

My mother is American, and my father is French; they split up when I was about 3 months old. I grew up speaking one language exclusively with one half of my family in New York and the other language with the other in France. It’s a standard of academic literature on bilingual people that different languages bring out different aspects of the self. But these were not two different personalities but two separate lives. In one version, I was living with my mom on the Upper West Side and walking up Columbus Avenue to get to school. In the other, I was foraging for mushrooms in Alsatian forests or writing plays with my cousins and later three half-siblings, who at the time didn’t understand a word of English. The experience of either language was entirely distinct, as if I had been given two scripts with mirroring supportive casts. In each a parent, grandparents, aunts and uncles; in each, a language, a home, a Madeleine.