Mohamed Abdeslam was speaking to French BFMTV after meeting Salah in his Belgian prison cell where he is awaiting extradition to France.
"There would have been more victims had I done it," Salah told him. "Luckily, I couldn't go through with it."
The gun and bomb attacks on a concert hall, a stadium, restaurants and bars on 13 November 2015 killed 130 people.
Abdeslam, 26, was arrested last month in Brussels four days before bomb attacks in Brussels killed 32 people.
Police believe the same militant network was behind attacks in both cities.
The French national, born in Belgium, had apparently been hiding in the Belgian capital for more than four months.
After his arrest, Abdeslam was initially questioned over his alleged role in the Paris attacks.
But after the suicide bombings in the Belgian capital, he chose to exercise his right to silence.
After meeting him in the Bruges prison, Mohamed Abdeslam said his brother had told him he wanted to co-operate with French authorities because he "is accountable to the French, but not to the Belgians" - a reference to the Belgian attacks.
However, Belgian authorities say Abdeslam has links to at least two of the Brussels bombers.
His fingerprints were found in a flat rented by Khalid el-Bakraoui, who blew himself up on the Brussels metro station on 22 March.
Investigators say Najim Laachraoui, named as one of the two Brussels airport bombers, was stopped by police in a car with Abdeslam on the Hungarian border with Austria in September.
Both the Paris and Brussels attacks have been claimed by so-called Islamic State.
Surviving Paris attacks suspect Salah Abdeslam chose not to blow himself up to save lives, his brother says.