Re the marriage, you would need to have some idea of where this may have taken place to do a search, and check if records exist and are available online or elsewhere - if Bray or South Co. Dublin are possibilities then the place to check is RootsIreland (pay-website).
Some of the south county Dublin RC parishes are on IrishGenealogy - e.g. Sandyford, Rathfarnham etc
p.s. are you sure your Pearsons were RC ?
They vast majority on the 1901 census are non-Catholic - mostly CofI & Presbyterian, but also CofE and Methodist
Shane
Good questions Shane.
My evidence for them being RC is from several sources. First, my GGgrandmother, Bridget, known to be daughter of a Richard Keegan and believed to be the daughter of Richard & Charlotte married someone who was CoI and they were married in the Register Office - I had assumed that this was because it was a "mixed" marriage but could be wrong.
However, several years later an Anna Keegan, then living at the same address as Bridget, married a John Walsh in a catholic church. She gave her parents names as Richard Keegan and Charlotte Pearson (from which I deduced them likely to be Bridget's parents too, although by then both were deceased).
Also the Richard Keegan & Henrietta Kavanagh who married at St Catherine's (RC) seem to be the most likely couple to be the parents of one of the infant Richards buried in the same grave as Charlotte. Whether he is indeed the same Richard as Bridget's father or perhaps his son, this supports the likelihood that the family was catholic.
The ages of the infants buried with Charlotte indicate that the family must have been in Dublin from 1852 at the latest to at least 1866 and had several children in that time whose baptisms are not on the irishgenealogy site. This includes at least two births to Richard & Henrietta recorded on the FamilySearch site (IGI entries and Registration indexes).
As the burial addresses at Glasnevin, indicate North King Street and North Brunswick Street, I would think this is a bit far for St Paul's, Arran Quay, to be their local Parish. Are there any other "missing" parishes in that area of the city, which might be more likely?
I should note here that my "unsuccessful" searches of St Paul's registers on my last visit to Dublin included not finding some entries for which I had been given exact dates, on the pages that matched those dates, and also not refinding (for printing) one entry that I had previously found and noted details of. After coming away, I surmised that there may be multiple registers for that parish covering the same dates on different films, so need to go back and try again on my next Dublin visit!