The Netherlands, despite being tiny, has 4 official languages (Dutch, Frisian, Dutch Low-Saxon, and Limburgs). We also used to have a different dialect for each city, so you could hear something else every 10 minutes driving! But only a handfull of dialects are left nowadays.

Everyone in the whole country speaks Dutch (al be it with slightly different accents), so that’s one common everyone has. In the areas with local languages it depends. In Frysia, Frysian is spoken a lot and used in by the local goverment as well. Dutch Low Saxon and Limburgs are in an kinda odd situation. They where dying and only got officially recognised not that long ago, but thr native speakers left are proud and like to preserve. However, it has a weird status where the local goverment isn’t allowed to use it despite being recognised. While it’s spoken in many people in more rural areas, there are also people from those areas who can’t (especially in cities) or who mix the local language and Dutch. What is spoken together depends on whatever both people speak: if it’s the local language they use that, if it’s half/half they use that, else they use Dutch. People who mix or speak a local language might end up teaching their partner some mixed speech too.

Then we also have a lot foreigners who don’t speak Dutch, especially in the bigger cities (like Amsterdam, Rotterdam, Utrecht, Den Haag) and villages around them. About half our population is foreign. Due to that, it’s not uncommon for people to switch to use exclusively English despite it not being an official language. However, older Dutch natives don’t always speak English very well, and the more rural the less common English becomes.

We’re quite international oriented here. On top of previous languages listed, almost all Dutch people will learn at least 2 more foreign languages in high school; often French and German. However, those are rarely used unless we need it to talk to a native speaker. Similarily, we learn foreign languages if we’re interested or it’s useful to us. I for example have had some formal education in Japanese and Mandarin during my time in university, and want to learn more Cantonese and maybe Vietnamese as well.

What parents speak to their kids also depends on the combination of languages the parrents speak.

An example of how that works in reality (our first kid is due to be born late November):

I’m Dutch from the area we speak Dutch Low-Saxon, and natively I speak the local language and Dutch (outside of learning both, my dad’s side of the family speaks the local language while my mom’s side speaks Dutch). My partner is Chinese-Vietnamese (his grandma left China for Vietnam) with a Dutch passpoort (1st generation). He speaks some Dutch but it’s limited. We usually speak English, but try to use Dutch as well so he can practice. However, I also use Dutch Low-Saxon words with him (for example “skotteldoekie” instead of the Dutch “vaatddoek”, “siepeltie” instead of “ui”, etc etc).

My partner speaks Vietnamese and Cantonese originally, but while he mixes them with his family he rarely mixes it with Dutch or English. We do use some words, mainly when they’re more specific than their common translation or have none at all. Think a “chi gold” (chi is a measurement unit; 1 chi is roughly 3,75mg) or “lap cheong” (a type of chinese sausage, often translated to simply “Chinese sausage”).

We plan to both speak our local language (Dutch Low-Saxon and Cantonese) to our kid. Since Dutch is used all around they’ll hear that from us too when speaking indirectly, and since we speak English regularily that will be heard as well.