The Australian Cemetery Index shows 3 Austin burials at Carcoar.
John AUSTIN, d 19.6.1869, aged 80 (thus b abt 1789)
[Son of Edward AUSTIN and ??, M, (Wife unknown, married in England)
Died Mandurama Creek, Carcoar
Bur C of E, Carcoar]
John AUSTIN, d 8.8.1906, aged 83 years (thus b abt 1823)
[Son of John AUSTIN and Ann DEEN, M Margaret Winterbottom
Carcoar, Died Carcoar
Bur C of E Carcoar]
Margaret AUSTIN, d 15.6.1898, aged 66 years (thus b abt 1835)
[Dau of John WINTERBOTTOM and Rosanna SPENCER, M John AUSTIN
Carcoar, Died Carcoar
Bur C of E Carcoar]
The younger John Austin is of an age to be the son of "your" John AUSTIN. TROVE has a short mention of the younger John,stating that he was one of the pioneer residents of Carcoar.
https://trove.nla.gov.au/newspaper/article/71539988Judith