I have alot of info on descendents of Mat O'Brien and Mary Daly - my great great grandparents, it seems to tally with your info in some ways, but also seems to contradict...
they had a son called Mat O'Brien born in Meath in 1875, maybe this is where the lines cross??
my info is as follows:
from familysearch we have following children born to Mat O'Brien and Mary Daly
Philip – Bailieborough, Cavan – 13 Feb 1867.
Patrick – Bailieborough, Cavan – 13 Mar 1868.
Thomas – Ratoath, Meath –26 Feb 1872.
Mathew – Ratoath- 18 Apr 1875.
James – Fairyhouse – 14 Nov 1878.
Maria – Fairyhouse – 17 Jan 1881.
The O'Briens moved to Killeigh sometime before 1901 census. in 1901 census, Mary is a widow living with children Anne, Thomas, John & James
http://www.census.nationalarchives.ie/pages/1901/King_s_Co_/Killeigh/Ballinvalley/1469401/Another son, Patrick lives nearby
http://www.census.nationalarchives.ie/pages/1901/King_s_Co_/Killeigh/Gorteen/1469470/Patrick's marriage certificate in 1893 confirms that his parents are Mat O'Brien and Mary Daly and the family were living in Killeigh at this time.
Mary's death in 1911 shows the informant was Teresa O'Brien, daughter