Searching Cornelius Donovan my 2nd Great Grandfather

My name is Karen (Donovan)Lannan, from New Brunswick Canada and I am searching for any information on my paternal Great Great Grandfather Cornelius Donovan who was born in Ireland. Family believes he was from Limerick . He was born in 1793 and married Johanna Barrett, his 3rd cousin (b.1797). They immigrated to New Brunswick, Canada in 1818, arriving in Pokemouche and bought a piece of land in 1821 according to Land Petition and 1851 NB census.  They traveled from Limerick to Waterford and possibly sailed from there. They travelled with Thomas Barrett (Johanna Barrett's brother) and his wife Mary Hallihan.  Cornelius and Johanna were married in  PEI , June 30th , 1840. We think this may have been  a convalidation of an existing marriage that took place in Ireland. They received a dispensation of consanguity in the 3rd degree meaning they were 3rd cousins.  Their first child John born July 8, 1820 died young. 2nd child Michael b 1823, Mary b.1825 ,John C, 1827 (my grandfather) Cornelius 1829. There were 3 other Donovan familys who migrated from Ireland to Renous, NB. We believe them to either be Cornelius's brothers or cousins. Timothy Donovan b 1777 Ireland. D. 1861 -1871 In Renous, John Donovan b. 1796 Ireland and died 30 April 1830 Renous Married to Anne Walsh., Michael Donovan Born 1799 in Drimoleague Cork Ireland. Married Ellen Butler. He died Oct 31, 1883 Renous, NB, Canada. In the St. Bridget's RC Cemetery in Renous, NB, where all these Donovan's are buried also is the headstone of a Jeremiah Hallihan 1787-1875 (possibly brother of Mary Hallihan wife of Thomas Barrett) mentioned above.The inscription on headstone says Jeremiah was from Bandon, Ireland, Parish Desert, County Cork. Based on information my brother receivedt the names Donovan, Barrett and Hallihan surnames all existing in Cork in the same town could be Clonakilty.    My husband & I and family were in Ireland last June 2012 and spent 3 weeks travelling the areas of my ancestors but did not find any new information. Anything you can find to assist in my search would be greatly appreciated. We hope that Cornelius Donovan had other siblings who remained in Ireland and that their ancestors are living there today. Would so love to make a connection or to even find a picture to put to the name. Even information on the great great grandparents of Johanna Barrett who would also be Cornelius"s great great grandparents as well. My Dad was Allan Donovan, his dad Francis Donovan, his dad, John C Donovan, his dad Cornelius Donovan.  Thank you so much in advance to anyone who can give me a lead. You can reach me here or  at karenlannan@hotmail.com