I never had a problem. I tried blagginh my way in to BNE DOM, with my sister, her two kids and my mother, and was told at reception "We would never deny a family access" - I think she presumed my sister was my wife.
Also got into SYD T3 when I was doing SYD-MEL, connecting onto QF9, and Mum and nephew (aged 6) were allowed in, they even let Mum pop out from time to time to get cancer (luckily she has since given up).
IME, they have always been pretty good at QF, unlike BA.
Dave