Hi Sean,
Thank you for your message. I hope that someone with information makes a connection with you and helps you to further your research.
In the meantime, have you tried also looking at Church records for more information? Most Catholic records are held locally so you may need to write to the local parish priest for possible assistance. One website that you may find useful is the Irish Times where they give an overview of what records are available in specific parishes. It also shows you where copies of the records are available. For Haggardstown parish, follow this link:
http://www.irishtimes.com/ancestor/fuses/rcparishmaps/index.cfm?fuseaction=showidrecords&CityCounty=Louth&parish=Haggardstown&churchid=215
For Dundalk:
http://www.irishtimes.com/ancestor/fuses/rcparishmaps/index.cfm?fuseaction=showidrecords&CityCounty=Louth&parish=Dundalk&churchid=216
Most surviving Church of Ireland records are still held by the local clergy, although some are in the National Archives of Ireland and others are in the Representative Church Body Library in Dublin. Here are their websites: http://www.nationalarchives.ie/ and http://ireland.anglican.org/about/42
Lists of these surviving registers can also be found at the National Library of Ireland.
Have you looked for the family in the 1901/1911 census records? If not they are available online here:
http://www.census.nationalarchives.ie/search/
You could also try looking for some record of the Brennan/Hughes families in Griffith?s Valuation. This is a property valuation survey carried out in Ireland 1848-64 and is available online here:
http://www.askaboutireland.ie/griffith-valuation/
Some other websites that you may find useful are:
The National Archives of Ireland http://www.nationalarchives.ie/genealogy1/genealogy-records/introduction/
The National Library of Ireland http://www.nli.ie/en/family-history-introduction.aspx
The Public Records Office of Northern Ireland http://www.proni.gov.uk/index/family_history.htm
Irish Genealogy Tool kit: http://www.irish-genealogy-toolkit.com/
Genealogy links: http://www.genealogylinks.net/uk/ireland/louth/index.html
From Ireland: www.from-ireland.net
Best of luck with your research!
Genealogy Support