Seems to be much more common as a thing with children who haven't finished acquiring both their L1 and L2 (as in multilingual) while still going through the bio

Seems to be much more common as a thing with children who haven't finished acquiring both their L1 and L2 (as in multilingual) while still going through the biological sensitive period where you have to acquire language. https://en.wikipedia.org/wiki/Language_attrition#Age_effect https://en.wikipedia.org/wiki/Language_attrition#Age_effect