Dear Kieran
Welcome to Ireland Reaching Out and apologies for the delay in replying to your message.
Do you have any dates around which you could conduct a search?
As you can see from the link below, Brosna is a Civil Parish in Co. Kerry:
http://www.irishtimes.com/ancestor/fuses/townlands/index.cfm?fuseaction=TownlandsInCivil&civilparishid=1109&civilparish=Brosna&citycounty=Kerry
Records for the corresponding Roman Catholic Parish of Brosna begin in 1866. There are some places where you can search online, however these websites do not have complete collections and many do not cover the period after 1900:
www.familysearch.org has a huge database of genealogical records including some church records for Ireland
http://churchrecords.irishgenealogy.ie/churchrecords/ have begun a project to upload Irish church records to their site free of charge. However so far only Counties Dublin, Kerry, Carlow and parts of Cork have been covered
Post-1900 parish queries should be addressed to the Parish Priest: http://www.mylocalnews.ie/kerry-15/brosna-414/church-4/roman-catholic-20/st-carthage-church-475/
Have you tried researching the immigration records for NZ for your ancestor?s details?
Remember to post any new information that you find here. The more information you post, the more likely it is that one of our volunteers will be able to advise or assist you. Also include information concerning which sources you may have already used so others may further your search.
Best of luck with your search
Clare Doyle
Genealogy Support