Diana, you need to thoroughly explore Australian records before starting with the IoM. If a second child was given the same name in a family it usually meant that the first child had died, not "disappeared" (with the exception of half-brothers or half-sisters sometimes having the same forename, but this was usually made clear in records).
What is the source for b.1823 in Andreas?
The 1837 bapt on the IGI is an extracted record (from the parish reg.), but the 1823 one is submitted by a member of the LDS Church, and may or may not exist.

You need to know who you are looking for from his passenger details, and certs of his marriage and death in Australia, as well as his information given on his children's birth certs.
If you have these details, please put them on the message board?

Sue