Sometimes known as Kate Ryan, Catherine Ryan, Catherine Taylor.
Kathleen/Kate/Catherine aren't unusual variants, but in what records is her name listed as Catherine Taylor?
<i> May have lived in the St George Qld area with a Mrs Kelly prior to this.</i>
Prior to 1915, when exactly? Have you been able to identify Mrs Kelly?
<i>She lived in the Yuelba area from about 1901.</i>
Again, sources?
It's interesting to look at births for this couple - I can see the marriage in 1915 (middle name Rowland), but the births trail says something else (parents names in brackets)
1908 Alice Byrnes (John Roland and Kate nee Ryan)
1910 Hazel Ryan (Kate Ryan)
1914 Kathleen Ryan (Kathleen Ryan) - married as "Ryan known as Byrnes"
(Alice and Hazel Byrnes, sisters, are writing joint letters to Children's Corner in the Daily Standard in 1923)
Death records show also a 1971 death for Florence Upton, parents John Rowland Byrnes and Kathleen Ryan, possibly she was born later (past the freely available births?) Were there any more children you know of? Was there a reason for the delay to the marriage?