Now, following weeks of media speculation that their marriage had ended amid blazing rows, Mr Mandla Mandela has confirmed that his wife had an affair with his brother.
Nelson Mandela's grandson and political heir has banished his wife from their home after he discovered that she had given birth to his brother's baby.
Mandla Mandela, 38, was accused of bigamy when he married the teenage Anais Grimaud while still married to his first wife.
Now, following weeks of media speculation that their marriage had ended amid blazing rows, Mr Mandela has confirmed that his wife had an affair with his brother.
"The Mandela family has sent my wife Nkosikazi Nobubele Mandela [nee Anais Grimaud] back to her home after it was discovered she has been having an affair with one of my brothers," he said. "I confirm this affair resulted in a son that Nkosikazi Nobubele gave birth to in 2011."
The scandal is the latest in a series of controversies involving Mandla Mandela, whom Nelson Mandela anointed as his political heir. As well as being a South African MP, he is a chief in the important Thembu tribe and handles much of his grandfather's legacy.
As grandson of the universally revered 94-year-old Mr Mandela, he is also the public face of the family.
He married his first wife, Tanda Mabunu-Mandela, at a traditional ceremony in 2004. Six years later, he married Miss Grimaud, who is from the island of Reunion, a French overseas territory in the Indian Ocean.
On marriage, she took the tribal name Nkosikazi Nobubele Mandela.
The couple's son was born in September last year and was named Qheya by Nelson Mandela himself.
But the marriage was marred by the fact that Mandla Mandla remained officially married to his first wife.
Ms Mabunu-Mandela fought the Grimaud marriage in the law courts and it was declared unlawful last year.
In a statement released this week, Mandla Mandela said DNA tests confirmed that the boy was not his son but he did not identify which of his two brothers was responsible.
"The revelation of this affair has come as a shock to me and the rest of my family," the statement reads. "It has been made more painful because it is my own brother who is at the centre of the crisis."
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