Nelson Mandela’s relationship with the Clinton family reflects a genuine friendship, stemming from their matching personalities and the Clintons’ intellect, according to an insider account. “It’s quite noticeable how broad their view was of the world, how informed they all are — all three of them — about all details of the very small countries around the world,” Zelda la Grange, the woman who served as Mandela’s private secretary from 1997 until his death, said in an interview about her new memoir, “Good Morning, Mr. Mandela.”