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The eldest son of former Cuban leader Fidel Castro took his own life Thursday while living on the island his father ruled as president for more than 40 years.

Two Cuban government sources confirmed to NBC News that Fidel Angel Castro Diaz-Balart, 68, died on Friday morning following months-long treatment "for a deep state of depression by a group of doctors."

Fidel "Fidelito" Castro Diaz-Balart in 2015. Joe Raedle / Getty Images file

According to Cuban state media, Diaz-Balart had been hospitalized for his depression but was later released for outpatient care.

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He had been serving as the scientific adviser to the State Council and vice president of the Cuban Academy of Sciences.

Related: Fidel Castro's Death

Diaz-Balart, often called "Fidelito" or "Little Fidel" because of how much he looked like his father, earned a degree in physics in the former USSR.

He was known for studying how to develop nuclear energy on the island of Cuba, according to his official bio from the Academy of Sciences.

Cuban rebel leader Fidel Castro and his son, Fidel Jr., in 1959. AP file

The family has begun to make funeral arrangements, state media reported.

Diaz-Balart is the cousin of NBC News and Telemundo anchor Jose Diaz-Balart as well as current Rep. Mario Diaz-Balart, R-Florida, who is a staunch anti-Castro figure.

His uncle, Raul Castro, has led Cuba since 2008 when he took over the role of president of Cuba from Fidel Castro — who ruled his island home beginning in 1959, antagonized 11 U.S. presidents and died in 2016 aged of 90.