[1] He was the fifth child born to Patrick Alban O'Sullivan and his wife Mary Bridget (née Macgroarty), both of Irish Catholic descent.

[3] He served in the Royal Australian Air Force from May 1942 to December 1944, performing intelligence and administration in Australia and the South-West Pacific.

[2] He was commissioned as a flying officer and met future prime minister John Gorton while stationed at Milne Bay.

[3] O'Sullivan ran unsuccessfully for the United Australia Party (UAP) in the Division of Brisbane at the 1934 federal election.

[4] In his maiden speech to parliament, O'Sullivan spoke of his belief in the doctrine of natural rights deriving from God.

He was an anti-communist and cited the papal encyclical Quadragesimo anno in a 1947 speech against the Chifley government's bank nationalisation bill.