(CNN) -- First lady Michelle Obama met with former South African president Nelson Mandela Tuesday as part of a weeklong visit to the continent, according to a spokeswoman for the first lady. Accompanying her on her visit with Mandela were her nephew Avery Robinson, 19, and niece, Leslie Robinson, 15, children of Obama's brother, Craig Robinson, according to Semonti Stephens, deputy communications director for Mrs. Obama. Obama was expected Tuesday to began visiting other luminaries in the country after arriving in Pretoria on Monday night. Obama, traveling on what officials have said is her second solo official visit to the...