Martine,
Elizabeth replying for Bert - I am the family genealogist (Bert's spouse).
The birthdates for the children of John McCarthy came from Canada Census and burial records (all died in Montreal). They are based on age at the time of census/burial and so are approximate.
The reason for searching in county Kerry is the marriage records for Jeremiah (Montreal 1852) and Michael (Montreal 1860) state John and Mary Brennan being from county Kerry. The marriage record for Daniel (Montreal 1870) states John and Mary Brennan being "of this parish" - Notre Dame de Montreal. Catherine never married and died in Montreal 1893.
Have not as yet found passage records for the children or for John and Mary Brennan. However, the 1901 Canada Census shows Michael immigrated 1850 and Daniel 1860. Presume John and Mary Brennan immigrated between 1860 and 1870.
I have searched the on-line Kerry Church (Catholic) records and did not find a marriage record for John & Mary or births for their children.
I am really at the proverbial "brick wall".
Any information/suggestions you can offer would be greatly appreciated.
Elizabeth