Living in Australia they would have to learn English. Explain to me exactly how one becomes bilingual through no merit of their own, I'd love to learn another language without doing any work.
We are not talking about English.
And very easy. Just have your parents move you to another country when you are say 5 and expect to pick up the new language without much difficulty. Or live in a country (like many in Europe) which have multiple languages (e.g Switzerland - German, French, Italian).
If you are brought up speaking two language - it is the easiest way for you to learn two languages.
It is therefore a privledge to have your parents do the work for you, since you can become fluent with barely any work on your behalf, but your parents.
But when you are the age we are now, or older, it is actually faster for us to learn languages then when we are a kid, just takes A LOT of work to reach the same level - very taxing.
If we compare the two, where one has to work extremely hard to get the same - definitely unfair for that person if they are up against a fluent speaker.
Though, there is nothing to stop this occurring, as i'm sure even if there were rules, people could easily lie and just win.