The Next Stop

Out of curiosity, of those who have been brought up in a cultured family (eg. chinese, greek etc), what do you consider your first language? I've always been unsure and usually say English, although I don't really think that is the case. I think I might have started English at kindergarten. Sometimes I feel that I am at a disadvantage because I don't participate much in all the Aussie culture and stuff, and have no clue what certain terms mean, or perhaps certain issues or basically anything in general. But then again, I'm a lot better off than those who moved to Australia to study, so I don't want to 'tip the scales' or anything. I'm just wondering what I should pick for future reference.