A branch of the southern Kennedys migrated to Co. Antrim at the start of the 17th century and many of the name in Ulster will be of this connection. However, many Ulster Kennedys are originally of Scottish stock, the MacKennedys being a branch of the Clan Cameron. This family produced the Lords Kennedy, later Earls of Cassilis. The surname is now also very common in Galloway and Ayrshire.
. The most famous modern bearers of the name are of course John F. Kennedy (1917-1963) thirty-fifth president of the U.S., and his brothers Robert and Teddy, descended from a Wexford branch of the Dalcassian family.
Jimmy Kennedy (1902-1984), of the Ulster Kennedys, was one of the most successful popular lyricists of the century, with such songs as "The Teddy Bears? Picnic", "Red Sails in the Sunset" and "South of the Border". He received an OBE in 1983.
Sister Stanislaus Kennedy (1939 - ) is an outspoken campaigner for the poor and the homeless in Ireland.
Sir Arthur Kennedy (1810-1883), also of the Ulster family, had a long and successful career in the British colonial service, becoming governor of Gambia, Hong Kong, Queensland and West Australia.