John Morgan O'Kennedy was born in Clonmel (Irish: "honey meadow"). It is the county town and largest settlement of County Tipperary, Ireland. The town is noted in Irish history for its resistance to the Cromwellian army which sacked the towns of Drogheda and Wexford. With the exception of the townland of Suir Island, most of the borough is situated in the civil parish of "St Mary's" which is part of the ancient barony of Iffa and Offa East.

John Morgan O'Kennedy was the biological son of Joseph O'Kennedy and Elizabeth O'Kennedy and the foster son of John O'Kennedy and Esther O'Kennedy

John Morgan O'Kennedy's first wife died in Ireland. He was left with 2 sons & 2 daughters and moved to the Cape Colony with his 2 daughters; his 2 sons remaining in Ireland. In the Cape Colony he met and married Rachel Christina Mellet.