Anybody who was born outside of South Africa to a South African citizen. His or her birth has to be registered in line with the births and deaths registration act 51 of 1992.

South African Citizen by Naturalisation:

Permanent Resident holders of 5 or more years can apply for citizenship. Anybody married to a South African citizen qualifies for naturalisation, two years after receiving his or her permanent residence at the time of marriage. A child under 21 who has permanent residence permit qualifies for naturalisation immediately after the permit is issued.

Automatic loss of Citizenship

This occurs when a South African citizen:

Obtains citizenship of another country by a voluntary and formal act, other than marriage, or;
Serves in the armed forces of another country, where he or she is also a citizen, while is at war with South Africa.

Deprivation of Citizenship

A South African citizen by naturalization can be deprived of his citizenship if;

The certificate of naturalisation was obtained fraudulently or false information was supplied
He or she holds the citizenship of another country and has, at any time, been sentenced to 12 months imprisonment in any country for an offence that also would have been an offence in South Africa.

Acquisition of the citizenship or nationality of another country

Any person who wants to apply for citizenship in another country must apply to the Minister of Home Affairs to retain his or her South African citizenship before acquiring the citizenship of the other country.

Resumption of South African citizenship:

Any former citizen by birth or descent who:

Gave up his or her South African citizenship, or
Automatically ceased to be a South African citizen;

can apply for the reinstatement of his/her South African citizenship. However this person must return permanently to South Africa.