Thanks for that.
To be honest have no idea as to when he left Ireland.Assume it would be after 1890 or so going by his birth as being either 1871 or 1875.None of his siblings left Ireland so imagine he was 18 or so before he left.
He is not with his family on 1901 Irish Census.
http://www.census.nationalarchives.ie/pages/1901/Carlow/Agha/Rathedon/1038537/And no real possibilities elsewhere in Ireland that seem even plausible so assuming he left between 1890 or so and before 1901.
There is no record of him marrying in Ireland that I can find but of course its always a possibility he married in Dublin etc after leaving Carlow and before going to the US.
Commemorated here on family headstone;
http://www.rootsweb.ancestry.com/~irlcar2/Dunleckney_Graves_incriptions.pdfErected to the Memory of Philip Brennan of Ratheadon who
depd this Life March 15th 1840 aged 60 yrs. Also his Beloved
wife Mary Brennan who depd this Life March 20th 1861 aged
75 years. Also his son Thomas Brennan depd this life Nov 2nd
1839 aged 26 years. Also his son John Brennan Depd this life
July 2nd 1847 aged 22 years. And also his daughter Elizabeth
Dowling depd this life Aug 5th 1860 aged 40 yrs.
Erected in Loving Memory of Philip Brennan, Ratheadon who
died 5th April 1875 aged 56 yrs. Also his daughter Mary died
21st Nov 1894 aged 21 yrs. His son Michael died 3rd Oct 1914
aged 47 yrs. His son Patrick died in U.S. America 22nd April
1914, aged 40 yrs. Also his wife Margaret Brennan died 18th
Nov 1919 aged 83 yrs. His son John Brennan died 17th June
1942 aged 79 yrs
Love the way age's were so fluid at that time.He was 38 on US death cert(1875),40 on headstone(born 1873)42 on his memory card (1872)and Baptised in 1871.