JM,
Interesting info about the double entry-have wondered before, but never checked-thanks.
I have checked NSW BMD as follows, ignoring surnames to eliminate spelling variations, such as you have found
1 Marriages 1803-1817 ( based on aad 67=born c 1789)for anybody called Catherine, Catharine,Catherina, Catharina, Christina. No relevant groom name
2 Births 1788-1797 same names-6 hits, 4 canbe accounted for, and Currins and Kennedy would have been only 15 in 1811 when John born to Catherine andJohn McNally, and this does not fit with any subsequent indications of age.
Nice to have "Team Catherine" firing on all cylinders!
David
David