The 1911 Dublin census is online and shows Christopher and his family as you mention on Britain Place:http://www.census.nationalarchives.ie/pages/1911/Dublin/Moun...
There's an entry in the Ireland civil registration birth records index for Christopher Rourke in 1872 in the Dublin South Registration District. You can request the civil birth cert from the Ireland General Register Office http://www.groireland.ie
and click on "apply for cert".
Once you get his civil birth cert it will include his specific birthplace in Dublin South as well as his parents names including his mother's maiden name. You can then search for their civil marriage record when you have that detail.