Hi Sidewalk Surfer,
It's supposed to be within 6 months of the Birth Certificate being issued according to law.
That said, if the Consulado-Geral do Brasil in South Africa will legalize the on you have then it is really all you need. Once legalized by the Consulado the Cartório MUST accept it, they have no choice.
If once the Consulado receives the document, should they decline to legalize it then you would need to apply for a new Long Form Birth Certificate. That's the Birth Registration that shows not only your name, dob and place of birth, but also your parents' full names, dob, place of birth, etc.
Hope this helps you out.
Cheers,
James Expat-blog Experts Team