Mexico The two brothers couldn't be more different. Where Fidel is considered charismatic and impulsive, younger brother Raul is seen as pragmatic and reclusive.
But with the recent announcement that Fidel Castro was stepping down temporarily as Cuba's president after undergoing intestinal surgery, younger brother - and designated successor - Raul Castro has been shoved onto the world stage.
It is a platform that Fidel, almost 80, has commanded for nearly five decades, but that Raul, 75, has avoided.
As the spotlight shines on the younger Castro, the United States government, world leaders and ordinary people - especially Cuban exiles - will watch closely for any signs of what's likely to come in a post-Fidel era.
Most analysts and U.S. officials who have studied various post-Castro scenarios say they expect the small island 90 miles off Florida's coast to remain a socialist nation for years to come. And they look for Raul Castro to emerge as a pragmatic kingmaker of sorts, heading a collective leadership that will include military officials, policy makers, politicians and technocrats.
"We're witnessing the real thing," said Brian Latell, a former Central Intelligence Agency analyst and author of "After Fidel," a biography of Raul. "This is the succession. Whether Fidel is already dead or seriously incapacitated, I do not believe he will ever be back in power in full form again."
Communists seek stability
Cuba's Communist leadership launched a campaign emphasizing Raul Castro's revolutionary roots, attempting to reassure Cubans that the regime remains stable after Fidel Castro's hospitalization. The government said it would defend itself against any U.S. attempts to take advantage of Fidel Castro's health crisis after President Bush urged Cubans to push for democratic change, the Associated Press reported.
"Let's not exaggerate: Raul will not become Gorbachev because the democratization of Cuba implies its own destruction. But he could be an Andropov," Jorge G. Castaneda, a former Mexican foreign minister and an expert on Latin American leftist politics, wrote in Mexico City's Reforma newspaper. He was referring to the former Soviet Union leader Yuri Andropov and his protege and eventual successor, Mikhail Gorbachev.
What's certain, analysts say, is that Raul will not be able to fill the void that will be left by Fidel, an almost god-like figure who has shaped daily life in Cuba since he came to power on Jan. 1, 1959.
A different style
Raul Castro has no such aura. And he has a different style entirely from that of his elder brother. He's less authoritarian, said a senior U.S. official who analyzes the country's intelligence and security matters.
And as head of state, "he would bring in a different style of decision-making : a more corporate, collegial approach," said the U.S. official, an expert on Cuba's succession. Given his style, the official added, Raul might not be completely at ease as Cuba's maximum authority.
"He's the slap-in-the-back kind of guy and gets people to sit down and talk in the way Fidel can't. Fidel just turns off or yells back," the official said. "Raul is the reluctant leader. He's comfortable with being a minister. But he's not comfortable on the dais in front of millions of people. He's just not that sort of person. He's more comfortable behind the scenes working with friends."
Close ties to military
Where Fidel has maintained a tight bond with the Cuban people, Raul has been more pragmatic, cozying up to the military, an entity many analysts say is key to the survival of any new post-Castro government.
The armed forces "will either dominate a new regime : or, like the militaries in the former communist countries of Eastern Europe, be the willing accomplices in the demise of Marxist rule," Latell wrote in a 2003 study.
Younger officers unhappy with the pace of reform "could emerge as a powerful political wild card," he said.
In recent years, Raul Castro worked to turn the armed services into a moneymaker. The military soon was heading such state-run companies as Gaviota, which owns hotels, discos, restaurants, shops and charter services.
Fidel Castro himself played down talk of any internal conflicts after he suffered a June 2001 fainting spell, telling a crowd that the revolution would endure after his death.
"I didn't inherit any position and I'm not a king, so I don't need to prepare a successor," he said, even though he already had anointed his brother. "There won't be any trauma, and no transition is necessary."
Others aren't so sure.
Political exiles in Miami celebrated news of Fidel Castro's health problems last week with street gatherings and other events.
But in Mexico City, recent Cuban arrivals - self-described "economic refugees" - lamented the news not so much because they're huge fans of Fidel Castro, but because of the uncertainty around his illness.
"We're all concerned because Fidel is all we have ever known," said Vladimir Rojas, 34, outside El Rincon Cubano, a bar and restaurant near downtown Mexico City. "And for better or for worse, with Fidel you had stability."