Irish Research

I have never had need to do any Irish research before and am already baffled. Firstly, I know I have the right family from 1881 census up to 1911. The first child was born here c1880. How on earth though does the man go from being 28 in 1881, 40 in 1891, 47 in 1901 and finally 71 in 2011! His wife goes from 28, to 38, to 44 and finally 65.

My main problem though is how on earth to find a marriage or births for the children that were born there. Apart from saying born Ireland in 1881 and 1901, in 1891 it says both born Galray/Galway? Then in 1911 it says he was born in Carrigallen, which I find is in Co, Leitrim. She says born in Abagh-Cavanagh? Which I can’t find at all.
Sorry - should have said - it's the O'Reilly family - Patrick and wife Susan.

Is this an impossible task? For anyone who would like to see the census these are the links -

1881 -
http://ift.tt/1Lj8nPX

1891 - two pages as the family go onto the next page -
http://ift.tt/1P30A83

http://ift.tt/1P30A83

1901 -
http://ift.tt/1N8o7Hb

1911 -
http://ift.tt/1N8o666

Irish Research