I grew up bilingual: Korean and English at the same time.
I say my "first language" is whatever language is more prevalent.
so in the US: English. In Korea: Korean.
Even though they're both dominant for me, I tell people my dominant language is what we are speaking to make the person I'm talking to feel comfortable.
Unless, of course, we're conversing in something I'm not fluent in (Japanese, French, Spanish, ASL), in which case I will just say that I am bilingual English/Korean.
It used to be that I would remember everything in Korean or everything in English, and then become very confused by memories of English speaking friends speaking Korean when in fact they had spoke in English and it was only that I had remembered it in Korean. Or by memories of hearing certain Korean songs in perfect English, even though an English version doesn't exist.
In my dreams, everyone speaks whatever language they want but everyone can understand each other without a language barrier...
Sometimes I will remember a word in one language and then be unable to recall it in other languages (especially if I recall a word in Japanese or ASL that I need in English, because the words do not resemble English words in any way / aren't romance languages)
When I am counting stuff (like pages in a book) I will often choose to count in Korean if there are people around me speaking English and vice versa. It's less confusing for me this way.
