Actually it is quite common for extended families to join in Aus - I think this is one of the reasons the visa criteria are so strict. So, from what I read, a "dependents" visa is not necessily something that a true "dependent" can get - for example, my husband is certainly not "dependent" on me - he's got his own money - but he's still got a dependent visa, but if I had been supporting my Mum (as my husband does now, for example) she would not be a dependent if thought she WAS dependent on me....
All quite clear now. Just requires some Orwellian mind bending and reclassification of commonly used words....
Are they allowed to join when the first person is only on an employment visa. Yes the dependent thing is strange but its the same in the UK. We had a senior lecturer who was earning more than her husband. He lost his job, as his dependent she had to leave the country as well. Mad but the rules.
Amongst the eligibility is, presumably, not to have "moved to Hong Kong" more than two months before you ask this question.
You may not legally "move to Hong Kong" unless you have RoA, RTL, Unconditional Stay, or a visa permitting you to reside here.
Kashri
You mention on another thread that you've recently moved to HK from the US. Is your mother a US citizen? If so then she can stay for 3 months as a visitor. Why not just take her on a day trip to Macau? If she's retired and quite legitamtely appears to be taking a long holiday, I doubt there will be any issue with her doing that once or twice.