Condolences are being sent to former South African president Nelson Mandela after the loss of his youngest and last surviving sibling. CNN reports that the cause of Nokuthamba Mandela’s death is unclear. The 81-year-old passed away on Sunday around the same time Nelson Mandela was returning to Johannesburg as his Qunu home undergoes repairs.

South Africa sent condolences to Nelson Mandela on Monday following the death of his youngest sister and last surviving sibling out of 31 others. Nokuthamba Mandela, 81, died Saturday, South African President Jacob Zuma said.

The cause of death was unclear. “On behalf of myself, the people and government of South Africa, I would like to convey our heartfelt condolences to Madiba and the entire Mandela family at this difficult time,” Zuma said in a statement. “Our thoughts and prayers go out to you in this time of sorrow.”

The former president — affectionately known by his clan name Madiba — last appeared in public in the closing ceremonies of the 2010 World Cup in South Africa.

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