Castro Díaz-Balart's parents divorced in 1955, prior to the Cuban Revolution in which his father seized power in that country.

His mother moved to Miami, United States, with the Diaz-Balart family, taking her son with her.
Castro Díaz-Balart returned to Cuba as a child to visit his father, and remained there for the rest of his childhood.
In 1959, he appeared as a 9-year-old during an interview with his father on U.S. television.

Castro Díaz-Balart moved to Moscow (in what was then the Soviet Union), where he enrolled at Voronezh State University in 1968.
For safety, he studied under the code name "José Raúl Fernández", which he claimed to have chosen in homage to world chess champion José Raúl Capablanca and to have later used to publish 30 scientific publications.

He initially studied physical education before switching to nuclear physics in 1970.
He graduated from Lomonosov Moscow State University, and went on to work at the Joint Institute for Nuclear Research in Dubna, and to receive his first doctorate from Lomonosov, in 1978.
Returning to Cuba, he was placed in charge of Cuba's nuclear power program for a time, leading the Juragua Nuclear Power Plant construction program from 1980 to 1992, during which time he was also the executive secretary of the country's Atomic Energy Commission.
He served as a member of the Nonaligned Countries Movement's Coordinating Countries for the Peaceful Use of Nuclear Energy, and was elected to chair the Second Meeting of that group in April 1983.
Castro Díaz-Balart was removed from his positions in June 1992, following a falling out with his father, who cited "inefficiency" as the reason for the removal.
Castro then announced the suspension of construction at Juragua in September 1992, due to Cuba's inability to meet the financial terms set by Russia to complete the reactors.

Castro Díaz-Balart then returned to further his studies in Moscow, and received his second doctorate at the Kurchatov Institute of Atomic Energy in 1999.
In the 2010s, he returned to a level of prominence, serving as a scientific advisor to the Council of State, the governing body of Cuba, and as vice-president of the Academy of Sciences of Cuba.
Throughout his career, Castro Diaz-Balart authored articles on the developing role of nuclear energy.

In 2012, Castro Diaz-Balart disputed reports that Fidel Castro was becoming senile, describing his father as "lucid" and "working hard", which was similar to the "upbeat assessment" of Castro's health that Castro Diaz-Balart made in February 2007, following Castro's illness during that period.

In April 2014, he visited Russia to declare Cuba's recognition of the annexation of Crimea by the Russian Federation, also receiving an honorary doctorate at Voronezh State University.
In February 2015, during the Cuban thaw towards the end of the Obama Administration, when Americans were more freely allowed to visit Cuba, he participated in events to welcome American celebrities to the island, mingling with Paris Hilton and Naomi Campbell.
The following month, he visited Novosibirsk, Russia, meeting with the mayor, Anatoly Lokot, and regional governor Vladimir Gorodetsky to improve Cuban relations with scientific institutions in the region.
Castro Díaz-Balart's parents divorced in 1955, prior to the Cuban Revolution in which his father seized power in that country. 
His mother moved to Miami, United States, with the Diaz-Balart family, taking her son with her. Castro Díaz-Balart returned to Cuba as a child to visit his father, and remained there for the rest of his childhood. In 1959, he appeared as a 9-year-old during an interview with his father on U.S. television.
Castro Díaz-Balart moved to Moscow (in what was then the Soviet Union), where he enrolled at Voronezh State University in 1968. For safety, he studied under the code name "José Raúl Fernández", which he claimed to have chosen in homage to world chess champion José Raúl Capablanca and to have later used to publish 30 scientific publications.
He initially studied physical education before switching to nuclear physics in 1970. He graduated from Lomonosov Moscow State University, and went on to work at the Joint Institute for Nuclear Research in Dubna, and to receive his first doctorate from Lomonosov, in 1978. Returning to Cuba, he was placed in charge of Cuba's nuclear power program for a time, leading the Juragua Nuclear Power Plant construction program from 1980 to 1992, during which time he was also the executive secretary of the country's Atomic Energy Commission. He served as a member of the Nonaligned Countries Movement's Coordinating Countries for the Peaceful Use of Nuclear Energy, and was elected to chair the Second Meeting of that group in April 1983. Castro Díaz-Balart was removed from his positions in June 1992, following a falling out with his father, who cited "inefficiency" as the reason for the removal. Castro then announced the suspension of construction at Juragua in September 1992, due to Cuba's inability to meet the financial terms set by Russia to complete the reactors.
Castro Díaz-Balart then returned to further his studies in Moscow, and received his second doctorate at the Kurchatov Institute of Atomic Energy in 1999. In the 2010s, he returned to a level of prominence, serving as a scientific advisor to the Council of State, the governing body of Cuba, and as vice-president of the Academy of Sciences of Cuba. Throughout his career, Castro Diaz-Balart authored articles on the developing role of nuclear energy.
In 2012, Castro Diaz-Balart disputed reports that Fidel Castro was becoming senile, describing his father as "lucid" and "working hard", which was similar to the "upbeat assessment" of Castro's health that Castro Diaz-Balart made in February 2007, following Castro's illness during that period.
In April 2014, he visited Russia to declare Cuba's recognition of the annexation of Crimea by the Russian Federation, also receiving an honorary doctorate at Voronezh State University. In February 2015, during the Cuban thaw towards the end of the Obama Administration, when Americans were more freely allowed to visit Cuba, he participated in events to welcome American celebrities to the island, mingling with Paris Hilton and Naomi Campbell. The following month, he visited Novosibirsk, Russia, meeting with the mayor, Anatoly Lokot, and regional governor Vladimir Gorodetsky to improve Cuban relations with scientific institutions in the region.
Fidel Castro Díaz-Balart