Someone I know, a New Zealand citizen (born in NZ to NZ citizens), moved to Australia in late 90s, got married, had kids etc. (older teens and early 20s now). Husband and kids are all Australian citizens, and wife has recently (last 5 years) also become Australian citizen.
We were talking and she was wondering whether her kids might also be NZ citizens even though they've never lived in NZ (they've been there, on Oz passports, but only for holidays). And if so, do they need to do anything, or is it automatic and can they just apply for passports etc. if they wanted?