I have dual nationality NZ/British, my son who is 8 is British. Does we need visas?

I want to return back to Australia where I grew up and bring my soon to be 9 year old son. There is no listed father on his passport or birth certificate and I have 5 brothers who are Australian citizens.

Does he need a visa?

I am about to renew my own NZ passport from the UK to travel and enter on it.

Suggestions or website to research would be greatly appreciated.

Thank you

Lisa