my family history on my dad's side goes back through my great grandfather, an Edward Ahearn, born at Sydney in 1866. He was the product of James Ahern and Mary Maloney/Moloney, who came from County Armagh, They married at a Presbyterian church in Sydney in 1855/56, they had a heap of kids.
The name Ahern gradually changed throughout the generations and gradually became 'the norm' as Ahearn. I'm not certain as to whether James and Mary came as convicts or immigramts, as there are a number of them listed in records, without and definate link. Get in touch with me if you wish.
I have a heap of stuff on file and who knows? You may find something out!