Patrice Motsepe who is President Cyril Ramaphosa's brother-in-law and head of investment firm African Rainbow Capital said at a media conference the money would be channelled through the government to build water, health and education facilities.
The pledge follows a 1 billion rand donation each by the Oppenheimer and Rupert families, and a government package of more than 3 billion rands for industrial firms, and comes a day after the country lost its last investment-grade credit rating.
South Africa entered a 21-day lockdown on Friday with people restricted to their homes and most businesses shuttered.
