Hm, sounds like you will need to look into parish records for the areas in which relatives lived. I suggest reading the research guidance for Ireland at the LDS site:
http://www.familysearch.org/Eng/Search/RG/...est=E&Juris1=76From what I understand, if you are that far back in research in Ireland, baptisms, marriages, and deaths would all be kept by the churches.
I have a 4g-great grandfather born in Dublin in 1810, and I know I need to figure out what to do next! Do I look into EVERY church to see which ones were around in 1810? Or what? It is something I must learn about as well.