Raul Castro attends a rally in Havana, Cuba in this Jan. 24, 2000 file photo

Raul Castro is Cuban President Fidel Castro's younger brother and designated successor.  Leta Hong Fincher has more on the man who has temporarily taken over as communist Cuba's leader.

Raul Castro is 75 years old and widely seen as loyal, yet lacking his older brother's charisma.

Defense Minister Raul Castro has for decades been Cuba's constitutional successor. He has overseen some of Cuba's most important economic experiments with limited market reforms. Analysts say Raul Castro has also expressed interest in China's model of economic reforms.

But he is known as a staunch defender of Cuba's communist system. He made the following comments in 2002 near the U.S. naval base in Guantanamo Bay:  "We already know they don't like our social system, but it's a reality that we are here and plan to remain."

Raul Castro was born in 1931, five years after Fidel.

He joined a communist youth group even before the Cuban revolution. He fought alongside older brother Fidel in the 1950s to overthrow dictator Fulgencio Batista.

President Fidel Castro said he wanted Raul to be his successor three weeks after taking power in 1959. Raul took control of Cuba's armed forces the same year. Cuba's troops grew to be 50,000 strong under his leadership.

Raul Castro was heavily involved in Cuba's military conflicts with Angola and Ethiopia in the 1970s. He also helped revive Cuba's economy after the collapse of the Soviet Union in 1991.

Fidel Castro officially designated Raul his successor at a Communist party congress in 1997.  "The important thing is that Raul is fit. He has climbed the Pico Turquino [Cuba's highest altitude] and in very quick time,” said Cuba’s president.

Raul Castro is married to Vilma Espin, who fought with him during the Cuban revolution and is now head of the Communist Party-linked women's federation.