Juanita Castro, the younger sister of Cuban rulers Fidel and Raul Castro, who was a CIA informer and outspoken critic against their communist government, has died in Miami aged 90.
Florida had been her home since fleeing her homeland nearly 60 years ago.
Journalist Maria Antonieta Collins, who co-wrote Juanita Castro’s 2009 book Fidel And Raul, My Brothers. The Secret History, wrote on Instagram that she died on Monday.
“Juanita Castro was ahead of us on the path of life and death, exceptional woman, tireless fighter for the cause of her Cuba that I love so much,” Ms Collins wrote.
She said her funeral would be held in private. The cause of her death has not been made public.
A staunch anti-communist, Juanita Castro was so opposed to her brothers’ policies she became a CIA double agent under the codename “Donna”.
Raul (L) and Fidel Castro in 1996. The two brothers ruled Cuba for about 60 years
She wrote in her book she began collaborating with the CIA shortly after the United States botched the Bay of Pigs invasion in 1961. The wife of Brazil’s ambassador to Cuba persuaded her to meet an officer during a trip to Mexico City.
She told the CIA agent she did not want any money, and would not support any violence against her brothers or others.
She smuggled messages, documents and money back into Cuba hidden inside tinned goods.
The CIA communicated with her via shortwave radio, playing a waltz and a song from the opera Madame Butterfly as signals that her handlers had a message for her.
She had initially been supportive of her brothers’ efforts to overthrow dictator Fulgencio Batista, playing an active role in the Cuban revolution by raising money and buying weapons.
But she became disillusioned when Fidel Castro became a hard-line communist after taking power in 1959 and pushed those who disagreed out of his government.
Fidel Castro (R) in Havana in 1959 celebrating Batista fleeing Cuba
She remained in Cuba while their mother was alive, but fled the island after she died.
“Everything was becoming more dangerously complicated,” she wrote.
Raul Castro helped her get a visa to Mexico where she spent several months before going into exile in the US.
She never saw her brothers again.
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She helped found a CIA-backed non-profit organisation that worked against the Castro government before settling into a quiet life in Little Havana where she ran a pharmacy among her peers living in exile, who feared she was a communist spy.
She became a US citizen in 1984.
Fidel Castro ruled Cuba until 2008 – when he handed power over to Raul, who spent a decade as Cuba’s leader.
Fidel died in 2016 aged 90, while Raul, 92, is living in retirement. The eldest brother, Ramon, died in 2016 aged 91.