MVEZO, South Africa — A couple of decades ago, Nelson Mandela grew withdrawn while feasting with his family on Christmas Day in the part of rural South Africa where the antiapartheid leader lived as a child. Alarmed by the patriarch’s silence, some relatives looked at him and asked if anything was wrong.

“ ‘I’m just wondering what the rest of the community is doing while we’re having a huge meal,’ ’’ Mandela said at the time, according to his grandson, Mandla.