Note by Tony Leach - his birth location, Swartruggens, is not the town of that name in Northwest Province, west of Rustenburg (too early in the 1800's for this area to be visited by anyone but itinerant hunters/explorers). It is most likely a place whose name has changed, somewhere in the Uitenhage area, as this fits with other Doubell family locations, in addition to which several 1820 settlers' locations also indicates a 'Grootfontein, Swartruggens, Uitenhage' area somewhere close to Uitenhage. Better possibilities might be the Swartberg (mountains between Ladismith and Willowmore in the Cape), or Swartkops (a village 11 km north of Port Elizabeth, and so is close to Uitenhage).
Regarding Swartruggens, I see there is a note added in the overview by David Abraham Swanepoel:
Zwarteruggens was a field-cornetcy, in the district of Graaff-Reinet, adjacent to Uitenhage after the formation of the latter. It can be seen on a map in the source below, p.120 (PDF 145/645). The author cites another source for the map.
Swanepoel, Christiaan Hendrik. 2003. 'n Tak van die Swanepoel-familie in Suid-Afrika, 1699 tot 1999: 'n genealogiese en kultuurhistoriese studie. MA tesis, Universiteit van Stellenbosch. Free to download at: http://scholar.sun.ac.za/handle/10019.1/53526. File 64MB.
For me it seems clear he fits in here, using his Dutch ancestry and naming conventions, the names of first son and 2nd daughter ties up to his parents. It follows, if you can proof them, then you proof his parents.
I could not locate a Death Notice for him, whilst a baptism record / birth documentation seems unlikely in this case.