He was one of twin sons born to Grace Maria (née Plowman) and John Percy Sim.

He was then transferred to the 14th/32nd Battalion and served primarily in New Guinea, including as commander of a prison in Rabaul for suspected war criminals.

[1] After the war's end, Sim and his brother moved to Western Australia, attracted by lower land prices.

He first stood for parliament at the 1958 federal election, standing unsuccessfully in third place on the party's Senate ticket in Western Australia.

He travelled frequently overseas, including 13 trips to Indonesia, and was an advocate for the importance of the Indian Ocean to Australia.

[1] Sim crossed the floor on several occasions, including to support an Australian Labor Party (ALP) motion to amend the National Health Bill 1970 to increase federal benefits payable to hospitals treating uninsured patients and in 1977 to oppose two of the Fraser government's referendum bills.

[3] In 2006 he was awarded the Order of the Rising Sun (Gold and Silver Star) by the Japanese government in honour of his contributions to Australia–Japan relations.