Just summing up the births of John and his siblings:
1898/19252 Albert no father Ethel M mother Bathurst
1901/32896 Jack no father Ethel M mother Lithgow
1903/4259 Heba no father Ettie mother Lithgow
1904/13503 Victoria no father Ettie mother Lithgow
1907/6141 George no father Ethel M mother Newtown
Erin, you say that “the family story is that his father might not have been aboriginal but Ethel may have been”. As the father’s name is never recognised in the birth records, perhaps he (or both he and Ettie) was aboriginal.
Peter