We have Swiss (French speaking) friends who live in Aus. Their kids were born in Aus. They speak French in the house. The kids are fluent in French. The interesting thing is that, even though they speak French more around the house, the kids speak (and understand) English perfectly. They do better in English, at school, than the vast majority of their classmates who are brought up only speaking English.

Of course, if you're a native English speaker living in Australia, you're at a bit of a disadvantage in bringing up your children in, say, Spanish. These people naturally speak French, rather than English, so it's easy for them to talk to their children in French. It would take a lot of effort to speak to your children normally in Spanish.

But it's not impossible. In the Royal Family, traditionally they have all been native English-speakers but they've been brought up to become fluent in French and German.

I'm not so sure this is the case now. But when the Queen was a girl and when the Duke of Edinburgh was a kid, they were learnt French and German to very high levels.