South Africa’s only black billionaire last month became the first African to join Bill Gates and Warren Buffet’s Giving Pledge.

Patrice Motsepe, founder and executive chairman of African Rainbow Minerals, will donate half the income from his family’s assets to poor and marginalised South Africans. Motsepe is Africa’s eight richest man according to Forbes, with a net worth of $2.65 bn (£1.67 bn) in November 2012.

It is not clear how much money Motsepe will donate but funds will go to the Motsepe Foundation.

Motsepe said, “I decided quite some time ago to give at least half of the funds generated by our family assets to uplift poor and other disadvantaged and marginalised South Africans but was also duty-bound and committed to ensuring that it would be done in a way that protects the interests and retains the confidence of our shareholders and investors”.

Inspired by Warren Buffet, and Bill and Melinda Gates, who he met respectively in August and December 2012, Motsepe also cited the tradition of ubuntu, or botho, a Southern African ethic that focuses on openness to other people.

Explaining the concept, Archbishop Desmond Tutu has previously said: “Ubuntu speaks particularly about the fact that you can't exist as a human being in isolation. It speaks about our interconnectedness. You can't be human all by yourself, and when you have this quality – ubuntu – you are known for your generosity.”

Nelson Mandela has also spoken about ubuntu: “Ubuntu does not mean that people should not enrich themselves. The question therefore is: Are you going to do so in order to enable the community around you to be able to improve?”

Motsepe also cited religious values and a “responsibility and duty” to the poor as motivations for making the gift, which his children support.

Motsepe said his parents taught him about the duty of caring for the poor as well as about the importance of business and entrepreneurship.

He continued: “I was also a beneficiary of various people, black and white, in South Africa and in the US who educated, trained, mentored and inspired me and whose faith and belief in me contributed to my success in my profession, business and elsewhere.”

Motsepe and his wife Precious have contributed for many years to education and health causes as well as supporting women, young and disabled people.

He said: “Most of our donations have been private but the need and challenges are great and we hope that our Giving Pledge will encourage others in South Africa, Africa and other emerging economies to give and make the world a better place.”

The Motsepe Foundation, founded in 1999, will soon be guided by an advisory council of religious, women’s and labour leaders along with other respected NGO and community leaders.

There are four tiers of non-profit regulation in South Africa. Non-profit trusts can be established under the first. Primary regulators of charities in South Africa are the NPO directorate, the Tax Exemption Unit, the Companies Registrar, and the District Master of Court Office.