If that is your family in Swineford parish, you can see here that there are gaps in the years for available records.
https://registers.nli.ie/parishes/0133
You may never find out. Sadly that is part of Irish research. I have tried to follow your Bryan and John through censuses but none I can find which give more than Mayo or Ireland.
One of my Irish families was from Kilmovee, a parish adjacent to Swinford. They were in the same townland, on the same piece of land continuously 1840-1940 and probably for many decades before 1840. However I've found an entry in the baptism register for only 1 out of 5 known named children born over 23 years during the middle third of the 19th century. The family may have had more children who didn't survive childhood. Despite poring over images of the registers, finding rate remained 10% -20%. Registers either began too late, have too many gaps or illegible entries. Their parents were born sometime between 1810 and 1825 and there is no surviving baptism register for the parish in that period.
The family of my Honor/Annie lived in a townland in another parish for at least 70 years but I can't find her father's baptism (c.1830) and I can't tell which of half-a-dozen babies named Mary Walsh, born 1830's was her mother.
I can't find origin of my other Ann/Hanora ancestor or her husband. She was born at the time of the Great Famine and he was a child then.
There are many difficulties with Irish family history research. One is that the majority of the population didn't belong to the Established Church, the Church of Ireland which was the Anglican Church in Ireland. Another big one is the amount of records of all kinds which didn't survive.
There's advice + seminars + short courses online about Irish research. Today I received an invitation to a seminar.
