Juanita Castro, sister of Cuban leader Fidel Castro, sits next to a poster for her book "Fidel and Raul, My Brothers, the Secret History", during an interview with Reuters in Miami, Florida October 27, 2009. Using the code name Donna, the younger sister of Fidel and Raul Castro worked undercover for the CIA in Cuba in the early 1960s, helping opponents of their communist rule escape execution and imprisonment, she said in memoirs published in exile on Monday.