There’s a known phase where the kids will scramble the languages together.. by normal language absobtion they instinctively learn the differences but I believe the parents also influence it a lot with how much they might correct the children.
Source: I was raised bilingual and my parents were friends with another couple with kids, they were also a bilingual family but they were less strict in the languages so the kids developed slight accents and were somewhat weaker in the language that was not the main language of their school education. My brother and I had very strict parents so we are perfectly bilingual
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