Spent the weekend a few hours south with my parents and aunts, one of whom was visiting from Hong Kong. Because of the visitor, most conversation was in Cantonese. That was my first language, but I stopped speaking it once I was 7 or 8. However, if I listen carefully, I can still understand a fair amount.
It was somewhat exhausting, actually. I didn't participate in conversation as much as I normally do, and if I did speak up, it was in English (my aunt understands it pretty well, but is not comfortable speaking English). But eventually I had a really interesting revelation.
I don't translate Cantonese into English in my head. It stays in Cantonese, but I understand it.
My ability to speak Cantonese must be laying dormant, then, and all I need is practice. This is very exciting to me. I very much want to be able to communicate with my relatives, the majority of whom do not speak English. And I have always wanted to have bilingual children.
A week or two ago, Robin told me he wants to learn Cantonese. He does know a few words here and there (mostly names for Chinese food that he likes!) so I think it's possible we'll be able to do this. It will take years of work (especially for Robin) but we're gonna start now.