HAVANA, Cuba (CNN) -- Raśl Castro has lived all his life in the shadow of his older brother Fidel.
Raśl Castro has a reputation for ruthlessness but pushed for a move toward more capitalism in Cuba.
Even when Fidel Castro underwent intestinal surgery in 2006 and Raśl Castro became Cuba's acting president, Raśl didn't make a public appearance for two weeks, until after photos assured the country that Fidel was alive.
Smaller, less imposing and less charismatic than his brother, Raśl Castro has known for years that he was the man designated to take over. Yet the world knows fairly little about the longtime Cuban defense minister -- or what he would do as Cuba's new president.
"Is there going to be a transition here toward something?" Raśl Castro once commented to reporters asking about post-Fidel Cuba. "Yes, toward a better form of socialism and -- here's something you'll like -- toward a more democratic society."
What did he mean by "more democratic society"? The world may soon know. Watch how Raśl Castro has helped shape Cuba »
On Tuesday, Fidel Castro announced plans to resign as president and commander-in-chief of the country's armed forces after 49 years in power. It's widely expected that Raśl Castro will be named as the country's new president when the 31-member council of ministers meets Sunday.
Fidel and Raśl Castro planned the Cuban revolution together.
The brothers were born in Biran, the sons of a Spanish immigrant -- a rich landowner -- and the housemaid he eventually married. Raśl Castro was always by his older brother's side.
Together, they plotted the 1950s uprising that became the Cuban revolution, brought Fidel Castro to power and gave birth to the first communist nation in the Western Hemisphere.
After the collapse of the Soviet Union, which left Cuba on the brink of bankruptcy and starvation, it was Raśl Castro who insisted on allowing free enterprise farmers markets. He declared that "beans have as much importance as cannons, if not more."
Analysts say the world may see more of that pragmatism.
Six months ago, Raśl Castro began a "national debate" on the problems of the country, acknowledging high unemployment and other economic concerns.
Raśl Castro is "a man who's quite capable of showing flexibility when needed and quite capable of being hard-line when needed," said Harold Klepak, a professor at the Royal Military College of Canada. "So it will be what is best for Cuba. What's best, I think, in his mind for the revolution and its continuity."
Known as a fiery public speaker, Fidel Castro is said to be rather stiff in social situations.
Raśl Castro is seen as the more down-to-earth brother. He has a more common touch and enjoys parties and a good joke, according to those who have known him well. He's considered more the family man.
And sister Juanita, who defected to the United States in 1964 and lives in Miami, says it is Raśl, not Fidel, who is the patriarch of the Castro clan.
"He's kept the family together," said Ann Louise Bardach, author of "Cuba Confidential." "[Juanita] said he remembers everybody's birthday. He remembers everybody's anniversary. He goes to the graduations. He takes care of the gifts."
Still, in many ways, Raśl Castro is seen as more of a hard-liner than Fidel Castro.
During the early years of the revolution, the younger Castro earned a reputation for being ruthless with his enemies. Grainy black-and-white video shows him making impassioned speeches in the early days of the revolution.
Even before his brother announced his retirement, Raśl Castro said Fidel would be a hard act to follow.
"No one will ever again have as much authority as Fidel Castro has had, because of who he is, because he made a true revolution," 76-year-old Raśl Castro said.
Still, he says only the Communist Party can guarantee continuity.
And, as the architect of the Cuban army and its leader for 50 years, Raśl Castro has the military firmly behind him. E-mail to a friend