The Brennan Family came from Ireland in the mid 1800′s — likely from Kilkenny. In the mid 1800’s, Pierce Brennan emigrated to Canada.
The great potato famine occured in Ireland from 1845-1849 and the Irish left the country “in droves.” It appears quite possible that this is the time Pierce came to North America as he was born in 1923 (in Ireland) and first appears in the Canada census in 1951. A community of Irish immigrants established themselves in eastern Ontario as their stone workings skills were in demand for the building of Canada including the Rideau Canal.
This branch of the Brennan family is traced to Pierce Brennan born circa 1823 in Kilkenny, Ireland.
Canadian Census records