I think about this quite often, as 2 of my kids were born in Ireland, but grew up elsewhere (Slavic country). I speak English with them, but so do some of my friends/neighbors with their kids. The other kids would seldom speak English though, while my kids seem to default to English somehow. Btw. they left Ireland when they were 2y and 9months old (now 9 and 7), never attended daycare there, were only exposed to English at grocery stores, doctors etc. My point is, the early exposure to the language seem to make huge difference. I'm sure it's a combination of other things too but I'd say it is definitely a strong factor.
[edits: grammar]
CaptainOfCoit|4 months ago
> I speak English with them
You seem to know the answer already :) Kids regularly find "more reliable" adults and weight their opinion, manners and ideas higher than others, so if you're mainly speaking English to them, they'll default to trying to adopt to that, even if the main language is different all around them.