Thank you Patricia Jane Thomson, I just found on SAHC Australia's website that "Birth records date back only to the year 1901." Pity had hoped his ID number might lead to a breakthrough.
Private I've spent the last 18 years researching this family. South African Archives, FamilySearch, Cory Library at Rhodes. You name it, I've checked.
Annoying thing is I have an old newspaper article in which he states he was born in Grahamstown and raised in Port Elizabeth, and that he moved to Orange Free State with his parents as a teenager. However, no sign of his parents in Free State Archives etc.
I think it's mostly on account of our family name. Corrie gets butchered in every conceivable way: https://www.geni.com/projects/CORRIE-family-of-Kroonstad-Free-State-South-Africa/31940 (CORI, CORRI, CORRIE, CORRY, CORREY, COREY, CORIE. I've even seen LORRY and BORRIE!). If yDNA testing is to be taken at face value even GORRIE/GORRY is an option.