Rex Stewart grew up on hundreds of hectares of land at the family farm at Urunga. After moving to Redfern, with his parents and siblings Rex became the first Aboriginal student to attend Cleveland Street Boys' High School.
Stewart excelled at most sports and played for South Sydney President's Cup, in 1979 he coached the Campbelltown Warriors. Living in the Campbelltown area in New South Wales, Stewart had a long-standing association with the Tharawal Aboriginal Medical Centre in Airds, and also spent much of his time assisting Aboriginal youth who were caught in the judicial system in the Campbelltown area.