For starters, there are to separate (and totally unrelated) O'Conor/O'Connor tribes-- those in Connaught from which came the Irish High Kings and those in Kerry who have no royal pretense.

As kings of Connaught there developed in time two branches of the family, O'Conor Rua and O'Conor Don. The suffix of Rua (red) and Don (brown) referred to the colour of the hair of the two brothers who founded each of those lines. When the line of O'Conor Rua died out, the senior line (and hence the kingly line) became that of the O'Conor Don. In the 13th century the last two High Kings of Ireland were both O'Conor Don. In the 19th century the then O'Conor Don was officially recognized by Sir Bernard Burke, Ulster King of Arms, as the undisputed heir to the high kingship of Ireland. In the early part of the 20th century the style of O'Conor Don passed to Fr. Charles O'Conor Don, SJ, and upon is death to the eldest son of his younger brother, Denis O'Conor Don. The present O'Conor Don, Desmond, succeeded to the title "O'Conor Don" on the death of his father, the aforementioned Denis O'Conor Don. Desmond O'Conor Don is a retired international banking executive and presently resides in England. He has a son and grandson, as well as two brothers, both with children.

The title "O'Conor Don" applies only to the chief of the Connaught O'Con(n)ors, in much the same way that only a Scottish chief would use the style "of that ilk". In continental Europe O'Conor Don (never "The" O'Conor Don) is regarded as being of princely rank, and is often so styled. On page 29 of theScottish Clan and Family Encyclopedia there is a photograph of Lord Elgin (Chief of Clan Bruce) and late Denis O'Conor Don in which he is quite rightly styled "Prince of Connaught".