There is a Maria Magdelena Oosthuizen listed on the same church record as him in 1882, the same location he married in. As well as three people with his wife's surname Kruger (I didn't check the other pages).
Perhaps something on him might be revealed by researching her also.
"South Africa, Free State Dutch Reformed Church Records, 1848-1956", database with images, FamilySearch (https://familysearch.org/ark:/61903/1:1:Q2HL-1GVM : 4 November 2016), Rudolf Johannes Oosthuizen, 1882.