On occasions such as Anzac Day, we talk of brothers in arms in battles fought on the other side of the world. Recently, the sisterhood bonded when Australia's first female Prime Minister, Julia Gillard, told opposition leader Tony Abbott to check a mirror if he wanted to see what a misogynist looked like.
We share the sense of geographical location and distance from Europe and have similar historical colonial dynamics.
Like them, we take our sport seriously and go into deep national mourning when our teams fail to succeed and immediately look for someone to blame - usually the coach.
Both countries speak with a twang that foreigners find endearing and cute but hard to understand.
By contrast, Sydneysiders don't get about all dressed in gothic black, but some of them are a bit mad and can be seen playing energetic sports in the midday sun.
Last week, we had a heat wave with temperatures topping 40 degrees but I still saw a few crazed people exercising in the park. New Zealand sees itself as part of the Pacific island suburbs, while Australia sees Asia as its neighbourhood.
By temperament, we are similar in many ways but very different in others. New Zealanders often say, in disparaging tones, that Australians are a brash lot and much too full of themselves.
I think this is a misinterpretation of what is in fact a robust sense of optimism.
I have found Australians to be friendly, forthright, helpful and confident.
I am coming to the conclusion that this confidence comes from living on a vast continent and that size does matter. Sydney is home to more people than the whole of New Zealand. Australia straddles three time zones, with hugely diverse terrain and very harsh environments.
My theory is that the sheer size of the place could be intimidating to the national psyche if allowed to manifest itself. The map shows the majority of the population huddled together in cities around the coastal periphery with everywhere being a very long way from anywhere else. The only way to respond and cope with this huge geographical challenge is to develop confidence - optimism - she'll be right - a sense that it will all work out.
The dazzling ethnic mix of new immigrants I see catching the Sydney trains every day bring their own cultural contribution and wear it well in a country where optimism is a badge of confidence.
Terry Sarten is a Whanganui writer and musician currently residing in Sydney. Email feedback: tgs@inspire.net.nz
