Ask a sibling who the 'favourite child' is in their family and most will have an answer. Ask a parent, though, and they rarely will.
Favouritism is one of the many taboos of child-rearing, an admission that parents only tend to make to themselves, quietly, guiltily.
But Sydney father Davy Nguyen is one of the few who owns his favouritism. He has three daughters, aged 13, 18 and 20, and though he stresses that he loves and respects them equally, he has no reservations in telling them which he prefers.
That could be any one of them, at any given time.
See, Davy's favouritism is not fixed. It's a "reward system" dictated by his children's behaviour, and so it typically rotates every few weeks or so.
Sometimes, he'll be explicit and say, "You're my favourite right now because...". But he mostly expresses his preference with actions like encouragement or extra attention. And the others are given an explanation as to why they aren't being rewarded and the ways in which they can improve.
His daughters can fall out of favour for a range of reasons, including spending too much time on social media, not completing homework or assignments, not contributing to mealtimes, and being argumentative.
"I want them all to have a balance with everything that they do. Social media is good, but they need to focus on their studies... they need to be able to communicate," he told Mamamia.
"To me, it's about planting that mindset that if you really want something in life, you've got to work hard for it. And that is what I'm trying to do with my daughters; empowering them, giving them the right mindset, giving them the right training, the right tools, so that when they leave and go into the real world, they can conquer the world without any fear. They will have resilience."