Julian Charles Porteous was born on June 5, 1949, Sydney and baptised in Rose Bay Parish. He is the eldest of five children, having two brothers and two sisters. Archbishop Porteous has family links to Tasmania. His forebears arrived in Tasmanian from England in 1853. His great grandfather and great grandmother were both born in Hobart, within one kilometre of St Mary’s Cathedral.  His grandfather was named Manful Charles Hobart Granger.

Archbishop Porteous completed his primary education in Melbourne, Singapore and Parramatta before he undertook secondary schooling with the De La Salle Brothers at Oakhill College, Castle Hill.