O'Connell was born at Carhan near Cahersiveen, County Kerry, to the O'Connells of Derrynane, a wealthy Roman Catholic family that, under the Penal Laws, had been able to retain land only through the medium of Protestant trustees and the forbearance of their Protestant neighbours. His parents were Morgan O'Connell and Catherine O'Mullane. The poet Eibhlín Dubh Ní Chonaill was an aunt; and Daniel Charles, Count O'Connell, an Irish Brigade officer in the service of the King of France (and twelve years a prisoner of Napoleon), an uncle. O'Connell grew up in Derrynane House, the household of his bachelor uncle, Maurice "Hunting Cap" O'Connell (landowner, smuggler and justice of the peace) who made the young O'Connell his heir presumptive
