Hi Debbie
I was aware of the Isaac Carter - there is a good chance that he travelled under this name, there is also a good chance that he travelled under a completely different name if he was deliberately running away. His wife Sarah received a letter from him dated April 1859 in which he detailed many features of the country and of the conditions in the goldfields. That was the last she heard except for a report in the Braintree newspaper in 1868 wherein somebody reported that Frederick carter and party had unearthed a large nugget.
I don't know what to make of the sibling Emily. My thinking is that she may have died in infancy because she doesn't show up in any subsequent census
Jack