O'Higgins came from an Irish political family. His father was Thomas F. O'Higgins, a former leader of the Blueshirts and cabinet minister. His uncle was Kevin O'Higgins, the assassinated cabinet minister from the 1920s. O'Higgins's brother was Tom O'Higgins, a fellow TD and presidential candidate in 1966 and 1973. O'Higgins, his father, and his brother hold the distinction of all being elected members of the 13th Dáil in 1948.
He was married to Brigid Hogan-O'Higgins, also a Fine Gael TD. He married Brigid Hogan in 1958, one year after her election. They were the first married couple ever to be elected to the same Dáil. They had nine children. He died in 2005.