Yeah, there is just a little bit of rivalry between the Islands. Stewart Islanders think of themselves as Kiwis but Chatham Islanders do not. Hell, even in the Land of Ork people on Waiheki don't consider themselves to be Orks, Neither do many on the North side of the mighty Waitamata.
Bit like you I have friends spread out all over the place and both siblings are now Aussies. I suppose at the end of the day we are all Southerners to the Northern Hemisphere.