Sorry it has taken me so long to respond. I don't come on to this site much...obviously!
Are you a descendant of the first or the second family? My great-grandmother was Margaret, a daughter of the Captain and his first wife. I gather that when her mother died, and the Captain married the nurse, there was something of an estrangement with the first set of children. Alex's brothers had already come to Australia and settled around Sydney and Newcastle - they were not constantly to-ing and fro-ing, as he did - and I think Margaret followed them, as much as anything.
She had some children out of wedlock, one of whom was my grandfather. She married my great-grandfather Mark (who had been sent out to Australia by his English family to get him out of the way, and who had changed his name from Moses, just to confuse matters more). She then re-registered the children in his name. So it's really only an assumption that he was even their father...really.
Mark was an alcoholic who died when the children were still young. For whatever reason, she went to the country. Her life was hard scrabble I think from the moment she came to Australia...I don't know what she had to compare it to in Fiji, though.
I need to organise the timeline and so on a little better, I don't have any of my tree done properly, it's been at the scraps of paper stage for years now.
There is a memoir written by Alex about his life as a master mariner. Have you seen it? One of the New Zealand descendants transcribed it. You may already know of it, but I have a copy if you don't.