Here is an update with information that I have gathered:
William John Bleazby and his wife Maria Smythwick married in Gretna Green, Scotland 1826. The lived in Cork city before moving to Rosscarbery in 1835. They had 4 children - Samuel, Charlotte, William and Maria. Maria died in July 1872 and her husband William died in January 1881 at his residence at Bleazby Hall, Rosscarbery. Both are buried in the Church of Ireland graveyard in Rosscarbery.
Samuel died at an early age (I've yet to determine what age).
Charlotte Anne born 1833, never married, died in 1911. She lived with her sister Maria Beamish at the time of the 1901 Irish Census and was living in Doneen, Rosscarbery when she died.
Maria born 1840, married Richard Beamish, they had no children.
William John. junior was born in 1835, he married Catherine Baldwin Morris in 1857 in the Cathedral in Rosscarbery. He died in February 1912 and was living in Henry Street, Cork city with his wife at the time of his death. This property in Cork belonged to his father's sister Elizabeth and when she died in 1880 she left the property to her brother William John (senior) and her nephew William John (junior).
My parents live in Rowry House, Rosscarbery currently and documents found in the house reveal that in 1835 William J. Bleazby and a William Keohane from Rosscarbery were leasing the lands from Reverend H. Townsend. Rowry House was one of 3 houses named as part of the Townsend (Derry & Myross) estate.
From a Slater's Directory for County Cork 1870, it lists William J. Bleazby living at Bleazby Hall and a William J. Bleazby living at Rowry House. This suggests two separate houses. However, I can find no record at all of Bleazby Hall on OSI maps or speaking with people locally. Rowry House is known locally to all.
Further documentation found at home (Rowry House) shows that in 1901 when William Keohane died the house at Rowry and lands were assigned to his son Daniel Keohane. He lived and farmed at Rowry until 1926 when my great-grandfather James Connolly purchased Rowry House and farm. This property and farm has continued to remain in our family since then.
A letter that I found published in 1899 in the Skibbereen Eagle and written by William J. Bleazby (junior) contains the following "My parents brought me to Rosscarbery in September 1835, I have lived nearly all my life at Rowrie House and Bleazby Hall in Rosscarbery. I was educated in Rosscarbery College......" This confirms that they were two separate dwellings.
I hope this information is helpful to others. If anybody has any additional information to share about Bleazby Hall please let me know. I did contact the Landed Estates Database team at NUI Galway but they were only able to provide a small amount of information about Rowry House, they have no reference to Bleazby Hall.