Gosh I have to go to bed soon...
But one more piece of sleuthing. In an attempt to look at passenger records, I believe I have found the address of DdH's parents in the 60s and 70s. I am pretty confident it is them based on several records I found.
They lived in the suburb of Vaucluse, NSW and their occupations were listed as Company Director & Company Secretary and the address is linked to a development company which I suspect they owned. As I understand it, Vaucluse is one of the most expensive areas in Australia. The address they used to live at (unclear if the house has been rebuilt but it doesn't look super modern) most recently sold for $7.5million.
I wonder if RB found out about this and it was one of the reasons he pursued/stayed with DdH over all the years.
It also makes me even more suspicious of DdH playing dumb when it came to being a director/shareholder in the coin company. It stood out to me that she seemed very ignorant of company structures - I'm less inclined to believe that if her parents had a Pty Ltd company themselves.
Extra - their last address appears to have been in Narrabeen, another expensive Sydney area where houses appear to sell for around $3 - 5 million.