The Tithe records 1820-1839 are now available free:www.genealogy.nationalarchives.ie
I just read some info yesterday about the 'kings/clans/families of Ireland' prior to the Brits. It was in the history of a parish.
One of the oldest in Ireland. Killeigh, Offaly in the Union of Mountmellick. I just googled it. St. Mary's church. Might be worth a read.
The website is: www.killeigh.com