Aussie Family Relations (no spoilers)

Watching this movie, I (here in the US) get the impression that Phil is not Matt's father. Mainly, its because Phil calls Matt 'mate' and Matt calls phil 'Phil", but the mother 'mom'. Also, when Mom says to Phil this is none of his business (or similar), he freaks out like she is saying he has no say over Matt's well being.

Is it common in AU for kids to call their parents by their first name. It is not uncalled of, here in the US, but it is usually judged as strange.

This board gets so little traffic, be interesting how long to get a response, if ever!