Hi Alison,
I am a great grandaughter of Hannah - twin to Nancy and born in 1872. Catherine was an older sister and assigned to be caregiver to Hannah when she was born. Catherine and her husband, Michael Mannion, moved to Boulder, WA and took over the Exchange Hotel there in the 1890's. Hannah also went to WA although initially was in the South West of the state. She met and married John Costello, a miner, in Boulder and they lived near the Mannions. Nancy married in Boulder too, and the youngest brother James was in WA for some time. James is buried with Hannah in the Perth metro area. (Her husband had died 28 years previously and buried in Boulder.)
It is my understanding that David and Mary Croker came out at the suggestion of Redmond Barry who was a 'cousin' of Mary's. He was a colourful identity - plenty to read about, most famous as being the trial judge for Ned Kelly, but more notably in our family history as the trial judge for some of the Eureka Stokade trials. David and Mary had been heading to the USA; Redmond Barry suggested that they come to Australia as he thought some fine upstanding citizens could improve the public perception of the Irish after the rabble at Eureka. I have this information from three different sources; they seem independent.
David and Mary had some money and came out with unassisted passage to Melbourne and then travelled overland to South Australia. I don't think it would be correct to call them wealthy though.
I have two books about Redmond Barry; one by Ann Galbally has a partial family tree. (Family history was an interest of Redmond Barry's too.) Looking at this, Mary Moakly can not be a first cousin, but Doneraile is mentioned in relation to other branches of the family.
I have poked around a little; a sister of Redmond Barry's grandfather married the 1st Viscount of Doneraile in about 1752. They had a few children and a huge number of grandchildren, so maybe the Moakley was introduced through marriage somewhere here? Or elsewhere? It really is fishing and there is lots to trawl through.
An oral history done by my great uncle, a son of Hannah's, says that one part of the family went to the USA at the same time that David and Mary came to Australia. I assume this is a sibling of either David or Mary, but don't know which. This great uncle also says that the older members of the family (I assume he meant his mother's generation) corresponded for quite some time with the family that went to the USA, although it had been dropped by the time he was speaking - in the 1970's (and his mother had been gone for 30 years by then.)
There is a statue of Redmond Barry out the front of the state library in Melbourne; in the early 1960's an aunt of mine was visiting in Melbourne with her second cousins (descendents of Nancy) and they pointed it out as her first 'relative' (ie not ancestor) in Australia.
I would love to hear if you turn anything up.
Pauline