Looking at the 1901 Irish census there are just under 500 people named Kell(s).
http://www.census.nationalarchives.ie/search/
In Ulster they are almost all Presbyterian, Church of Ireland or Methodist (all of which point to their being of Plantation settler stock from Scotland & England).
We need a little more specific information about your family to trace them. What denomination were they, and when roughly did they leave Ireland? Do you know where they lived in Ireland beyond Ulster?