It appears to me that the Mary who married John Lynch was the daughter of Henry Pentland and his wife Julia. There is a civil marriage entry (Register of Births, Deaths and Marriages Ireland, Dublin South Marriages V2 #628 Jul - Sep 1899. John Lynch & Mary Bridget Pentland.) and also the RC record from St Mary's, Haddington Road, which would confirms her parentage.
On the family search website there are five user submitted genealogies (
http://familysearch.org/pal:/MM9.2.1/33N5-7SL), all of which appear to mirror each other but
try to shoehorn the facts into the scenario in which Matthew Pentland is Mary's father which we have now disproved. It does, however also give specific dates and places for John Lynch's birth and death. Clearly 24 July 2014 is an error for his birth but Rathganny, Westmeath, Ireland seems too specific to have been imagined and his death in 1934 in Dublin Ireland points to possibilities for further information on his parentage from civil records.
The difficulty with Henry Pentland and his wife Julia is that they were, if the marriage record is accurate in tense, living in Athboy in 1899 but there are no Pentlands in Athboy in 1901. there is an alternative spelling for Pentland, Pentleton which produces a result in 1901: Mary Cassidy, widow of George Pentleton and her son George but over the three generations of the family I have identified in Athboy there was no use of the forename Henry.
There is also some evidence of Pentlands and Pentletons being recorded as Pendleton and there is one Henry Pendleton recorded in the Tithe Applotments in 1830 a Lower Drumgill, Meath. More than that I have yet to find but will come back to you if I have any success.
