The 68-year-old son of Cuba's former leader Fidel Castro has killed himself in Havana, according to Cuban state media.
Fidel Ángel Castro Díaz-Balart was found on Thursday morning and is said to have suffered from depression.
The first-born son of the late president was nicknamed "Fidelito", or Little Fidel, because of the family resemblance.
He was a nuclear physicist, trained by the former Soviet Union.
"Fidel Castro Díaz-Balart, who had been treated by a group of doctors for several months due to deep depression, took his life this morning," Cuba's official newspaper Granma reported - little more than a year after his father.
State television said he had been receiving medical treatment as an outpatient in recent months, following a hospital stay.
At the time of his death, he was a scientific adviser for the Cuban Council of State and he served as vice president of Cuba's Academy of Sciences.
He headed the island's nuclear programme from 1980 to 1992, before it was suspended after the Soviet Union's collapse.
He was married to María Victoria Barreiro and had three children from his previous marriage - Fidel Antonio Castro Smirnov, Mirta María Castro Smirnova and José Raúl Castro Smirnov.
Fidel Castro Díaz-Balart was born in 1949, during his father's brief first marriage to Mirta Díaz-Balart, the daughter of a prominent pre-revolution politician.
His father went on to overthrow the US-backed dictator, Fulgencio Batista, in 1959 - when his mother's family fled the island and went to Florida.
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