Ok, well that's one theory out the window
.
I've found many cases where a young couple travel from the UK seperately, and meet up and marry in Australia. They obviously already knew eachother back home as they come from the same town. I thought this may be the case with your couple, but it doesn't seem to be so.
Death certifcates can help find 'missing' children, but I have cases where some have been omitted, so you have to keep an open mind.
The relationship could just be as simple as it looks - Robert and Mary might, for example, have met at work, paired up, had a baby, lived as man and wife to appear respectable, perhaps they fell out, went their seperate ways, and she marries someone else ....
