Yeslam Binladin, who at 54 is six years older than Osama, said in a television interview he believed his half-brother, thought to be hiding in the rugged mountains along the Afghan-Pakistan border, was still alive.
"I don't think he's dead," he said in the interview which was recorded on 28 May, but broadcast on Sunday.
When asked why US forces had still not been able to track bin Laden down, he responded: "I don't know, ask them."
Yeslam and Osama are among 54 sons and daughters of the late Saudi construction magnate Mohammed bin Laden, who had 22 wives.
His mother was Iranian, while Osama's was Syrian.
Bin Laden is believed to be hiding
along the Afghan-Pakistan border
The elder Binladin intentionally spells his name differently from his half brother, the prime suspect in the September 11 attacks.
In the interview, Yeslam said his brothers and sisters feared their father while growing up, a Saudi of Yemeni origin, who used to beat them.
Yeslam was educated in Lebanon and the United States and returned to Saudi Arabia after graduating from university.
He said he spent some time with Osama in Saudi Arabia between 1978 to 1981 before Osama went to fight alongside other mujahidin against the Soviets in Afghanistan. He did not mention seeing Osama after that.
The Swiss citizen - he has been residing in Geneva since 1985 - condemned the September 11 attacks in the US, and said he issued a statement following the attacks, condemning "all kinds of violence".
Yeslam said Osama, who did not leave Saudi Arabia to study abroad like most of his brothers, "was more religious than the rest".
"Osama didn't like music or TV and banned his kids from them," Yeslam said. "I grew up thinking this is weird, but he's free in his household and I'm free in mine."
Yeslam said that unlike Osama, he had no political interests and was never interested in the war in Afghanistan.
"I'm against all kinds of violence, resistance can take many forms without being violent. I'm against it and can't understand anyone who uses it"
Instead, he is passionate about flying, something he said he would never give up even though his father and one of his brothers perished in plane accidents.
"I would never let anyone in the world take away this right and prevent me from flying," he said.
Yeslam was married to a Swiss woman and has three daughters, but is now divorced.
Throughout the interview, said to be his first on Arab TV, he stressed he was against violence.
"I'm against all kinds of violence, resistance can take many forms without being violent. I'm against it and can't understand anyone who uses it," he said.