There is a church marriage for the couple in Kilmore Parish, Co Armagh on May 18 1862
This was just before the start of civil registrations
There appears to be two children's baptism to this marriage
John 17 May 1867 RootsIreland (transcriptions only) has the father as John Auston and Mary Quin and Julia 4 Feb 1869 father as John Austin
the sponsor on Julia's is Alice Quin, the informant on Cecilia Austin's birth is an Alice Quinn, the day and year fits but not the month but than the birth wasn't registered until May 1869.
Could Julia and Cecilia be the same person?
https://civilrecords.irishgenealogy.ie/churchrecords/images/birth_returns/births_1869/03399/2246543.pdf