All very very interesting, and mysterious. I hadn't spotted the anomaly with the date of James and his supposed son John Martin.
Any chance that we've found a convict?? John Martin's wife Annie was the daughter of convicts though not a convict herself
On John Martin Snell, this is all I have, which I've found looking at various other trees, so could well be inaccurate, I don't have access to any of the paid-for info like ancestory.
John Martin Snell was born in Sudbury, Suffolk in England in 1836. He worked as a labourer. He married Annie Lucas on 5th June 1862 at the Presbyterian Church in Warrnambool. His address at the time of marriage was the Temperance Hotel, Warnambool. He couldn’t sign his name, so made his mark on his marriage certificate. He died on 11th August 1909 in Winslow and was buried on 13th in Warrnambool cemetery.