If you are raising your children bilingually, sooner or later, a dominant language will emerge. While they might be able to communicate in both, there will be a language they prefer and a language they default to. It will most likely be the language they are more exposed to, that their friends speak and that they experience most of life in.
Even adults, who speak more than one language fluently, are not equally fluent it both, they will have times or topics in which they prefer one over the other. When I was pregnant with my first child, I sometimes struggled to tell my parents about it on the phone in German, since all Doctors visits and exams where in English and I had not been exposed to much of that topic while I lived in
. German-Greek friends of mine always go to Germany in the summer and thus the kids learned how to sail – and all sailing vocabulary that goes along with it – in Greek and would be hard-pressed to talk about it in another language. If you live in a country that speaks another language you are fluent in, it is only natural that you will expand your vocabulary exponentially there. To this day my specialized seafood and kitchen prep vocabulary is (only) in French, after working in a restaurant in Greece Corsica for 2 summers. Certain feelings will also be dominated by what language you experienced it in. A Russian colleague that lived in for his teenage years always thought about falling in love in French terms! Friends of mine, to whom I felt like an adopted daughter, would sometimes address me in Romanian in a very emotional moment, because that was their language of family connection. France
Finally, I could always tell I had assimilated to a point and started living in the other languages, when I started to dream in it…
When you have children, they will decide at some point, which language they communicate in to each other. If you have a mono-lingual household and a different-speaking environment, they will most likely stick with the inside-outside division of language. In the case of one-parent-one language, they might continue to switch, but more likely will eventually choose one - often the dominant language of the country they live in. (Thus my children by now communicate in English and only rarely switch to German, when I enter the room - they will, however, still always address me in German).
If your children start to show preference for a language that is not yours, it does not mean that they love you less. Of course you want them to experience the important parts of life in the language you grew up with, but that is sometimes impossible. So instead of looking at the loss - can’t recite the poems I grew up with, don’t read all the children's books I identified with, don’t hum songs from my culture when drawing, don’t have joyous outbursts in my language, don’t identify with my country’s team at the Olympics - try to focus on the gains – broader cultural understanding and being bilingual. I know it can be hard at times. If your child is asked whether they prefer to speak X or Y (which some well-meaning, interested strangers do), and they pick *the other* language, it can be like a stab in the back. But they don’t know that, they just say what they feel. If you move countries, the tables might turn to your favor. All you can do for now, is hang on to you language and connect it to as many positive experiences as you possibly can.