But even Mr. Castro, with his revolutionary credentials and fraternal connections, could not pull off all of the changes he had set out to make. Too many old-guard associates put up obstacles when they saw the widening inequalities that accompanied economic reforms. So although Mr. Castro is widely believed to be planning a move from Havana to Santiago de Cuba — on Cuba’s southeastern coast, the other side of the country — he is not expected to leave Mr. Díaz-Canel entirely to his own devices.
Mr. Castro was credited with strengthening institutional control and formalizing the concept of consensus governing. He believes in delegated authority. He has made sure that there are enough internal checks and balances to keep an eye on any successor with big ideas, while still watching this one’s back. Mr. Díaz-Canel was a handpicked successor, and it is not in Raúl Castro’s interest to see him fail.
“Raúl will be watching,” said Andy S. Gómez, a Cuba expert, now retired, who worked at the University of Miami. “Raúl, as first party secretary, will be not only watching him, but, more importantly, being there for him, symbolically, so he can move forward.”
Alcibíades Hidalgo, who was Raúl Castro’s chief of staff for a dozen years, believes that his former boss will hold on to power “until the day he dies.”
Alejandro Castro Espín, 52, is Raúl Castro’s son. Mr. Castro Espín runs the intelligence services for both the armed forces and the Interior Ministry. That is a big task in a country that works hard to stifle dissent and sniff out spies.
Mr. Castro Espín was part of the team that negotiated with President Barack Obama’s administration over restoring diplomatic ties with the United States, a sign that he is part of the most trusted inner circle.
But he also has serious anti-imperialist credentials: The title of a book he wrote in 2009, “Empire of Terror,” offers a not-very-subtle clue of his opinion of Cuba’s big neighbor to the north.
“The most important of the younger generation is Castro Espín,” said Brian Latell, a former C.I.A. analyst who has closely watched the Castro family. “I think he has a lot of influence with his father.”
Juan Juan Almeida, the son of a Cuban revolutionary war hero, grew up with Mr. Castro Espín and lived in his house when they were children. He said he was not convinced that his former best friend had the skills to succeed after his father dies.
“He’s powerful, but his power was given to him by his father,” Mr. Almeida said. “He will last as long as his father’s power lasts.”
Some experts believe that Raúl Castro would have liked to have made his son president, but that it would have looked bad internationally to have another Castro take over.
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Gen. Luis Alberto Rodríguez López-Callejas was a Castro by marriage — he used to be married to Raúl Castro’s daughter Débora, and is the father of Mr. Castro’s favorite grandson.
General Rodríguez is president of Gaesa, the holding company that controls the military’s business interests. The military runs all of the hotels and state-run restaurants, convenience stores and gas stations, making General Rodríguez one of the country’s most powerful men.
“He must have 1,200 companies under him,” said Guillermo Fariñas, an outspoken critic of the government who lives in Villa Clara Province. “I think the one who manages the country economically is him.”
Raúl Rodríguez Castro, General Rodríguez’s son, is Raúl Castro’s bodyguard, the kind of position that lends itself to knowing all kinds of secrets, Mr. Fariñas said.
Mariela Castro is Raúl Castro’s daughter. A member of Parliament, she enjoys an international and domestic following, largely because of her support for gay and transgender rights.
“Mariela is part of the scenery,” Mr. Hidalgo said. “She’s a decorative figure with a nice cause. In terms of power, she is far from the role of her brother or her ex-brother-in-law.”
Mr. Almeida said it boiled down to appearances.
“In terms of becoming a vice minister or joining the Council of State, I don’t see her doing that,” Mr. Almeida said. “The idea is to present a democratic face and erase the faces of the past. For the international community, they need to offer a nice friendly face of Cuba, which means not putting forth a Castro.”
Mr. Hidalgo, a former ambassador to the United Nations who later defected and now lives in Miami, does not think it will work.
“They are trying to give an appearance of change to what is fundamentally the same,” he said. “They are trying to continue Castroism without Castros in the near future, which is practically impossible.”