Retention of Citizenship

Any South African citizen who is 18 years and above and intends to acquire foreign citizenship without losing his/her SA citizenship, must apply to be exempted from losing his/her SA citizenship (Retain SA citizenship) before acquiring the foreign citizenship.

SA citizens under the age of 18 automatically retain their citizenship for life when immigrating. Unless they wish to acquire further foreign citizenship after they turn 18, they do not need to apply.
Keep in mind that SA citizens by birth that lost their SA citizenship always retain the right to Permanent Residence.

You automatically qualify for South African citizenship if: you are born in South Africa and at least one of your parents is a South African citizen or a SA permanent residency permit holder or if you are adopted by a South African citizen.