I am not sure I am following this properly, so I apologise if this is wrong.
I posted on the other thread re Limerick and have just seen this one.
There are some births to a couple Thomas Fitzgerald and Bridget Sheehan/ Sheahan in Limerick.
These are from the indexes and some have latinised names.
This one is before the marriage

Jacobum Fitzgerald baptised 17th March 1835 Shanagolden, Limerick
(James)
John Fitzgerald baptised 10th September 1836 St John's, Limerick city
Cathe Fitzgerald baptised 24th September 1838 St John's, Limerick city
Jacobus Fitzgerald baptised 13th August 1838 Shanagolden, Limerick
Mary FitzGerald baptised 12th September 1840 St John's, Limerick city
Patritius FitzGerald baptised 4th November 1844 Cahirnorry, Limerick
These could be checked with the Catholic registers.
The 2nd James and ‘Cathe’ would indicate that the Shanagolden couple and the City couple are not the same.
Heywood