Hi Peter , I did some work for a poster a few years ago , she was researching Kenna, and like you could not find people. On the Isle of Man the name changed to Kenaugh, Kennaugh, Kenah, Kennah, Kenagh, Kenniagh and one family became Keaney , basically anything starting with "K".

Basically I am saying to spread your search. If you know some of the childrens first names you can search on the IGI for just first names.

Cheers
David Dwyer