Can you please give attention to these questions as it will contribute to information that this forum can use to assist you.
* " i am unsure what john jun. middle name is. "
Where are you seeing your John FITZPATRICK named as John A FITZPATRICK?
* "Bridget married Patrick Coffey 26 nov 1873 Kapunda"
Can you please list all the information on this marriage certificate.
* How have you identified Bridget's family name to be KEARNEY...or variation of.
* Using TROVE I can see death of William FITZPATRICK, 1883. How have you identified this man to be your William FITZPATRICK?. It is hardly an unusual name.
* You had reason to believe there was a Patrick FITZPATRICK but did not have him to be on the "Tarquin" with his family. Apart from the reasonable suspicion that a FITZPATRICK family from Ireland might include a Patrick, where have you seen something specific for your family?
I can connect John FITZGERALD, died 1915, and Bridget COFFEY, died 1946, to be siblings in your family, so that bit is settled.