The following is from a file sent by a friend to whom I think I am distantly related through marriage with the O'Callaghans: (among other similarities I have a first cousin named Barbara O'Callaghan, not a usual Irish name).
Daniel O'Callaghan was born Abt. 1810 in Co. Cork, Ireland, and died Abt 1890 in Co. Cork, Ireland. He married Barbara Herberta Baldwin December 02, 1837 in Kilmurry, Co. Cork, Ireland, daughter of Herbert Baldwin and Barbara Dunne. She was born Nov 07, 1812 in Macroom, Co. Cork, Ireland, and died Abt. 1880 in Cork City.
There may be good reason for Barbara not to appear in Burke's since the Callaghans and Baldwins were bitter political enemies and the marriage is said not to have been approved of by the Baldwins.
There is also in a work 'Protestant Society and Politics in Cork 1812-1844', d'Alton, Cork, 1980, a table 'Some intermarriage patterns..' showing a Mary Baldwin, daughter of Henry Baldwin marrying Richard Tonson Rye in 1845.
I will ask my friend what her sources are and whether she gathered any other information on the Baldwin family.