Margaret Fagan b. 1849 is my great grandmother's younger sister.Her father, Patrick Fagan, is my great great grandfather.This is a record of my family.
Patrick & Mary (Matthews) Fagan had two older children, the first born about 1846, so their marriage would probably be around 1844 or 5.
Several records I have indicate that my Ma(t)thews kin were from Donore.The Fagans may have come from anywhere in the vicinity, maybe even from over the line in co. Louth.The records from Donore are sparse for the first decade of record keeping there, and no other vital events in the lives of my known ancestors seem to have been written down or preserved by the church in that parish.
I will have to investigate the other references to Fagans that you have cited here.