Tamerlan Tsarnaev practiced martial arts and boxing, even aspiring to fight on the US Olympic team.
Dzhokhar Tsarnaev had been on the wrestling team at a prestigious school and won a scholarship from his city to pursue higher education.
Neighbours recalled the ethnic Chechen brothers, living on a quiet street in Cambridge, Massachusetts, riding bikes and skateboards.
Yesterday, after hours of only grainy images of two men in baseball caps to go on, a portrait quickly emerged of the men, one now dead, suspected of carrying out Monday's deadly Boston Marathon bombing.
The brothers, who came from a violence-wracked Russian region, lived together and had been in the country for about a decade, according to an uncle, Ruslan Tsarni, who lives in the US state of Maryland. He said the brothers "grew up in Kyrgyzstan" - a Central Asian republic.
The strongman leader of Chechnya, Ramzan Kadyrov, said the two had no link to the Russian republic in the north Caucasus.
"They grew up in America, their views and convictions were formed there. The roots of evil must be sought in America," he wrote on his Instagram account.
Tamerlan was believed to be 26 when he was killed overnight in a shoot-out with police. He was the stockier one identified in video released on Thursday to the public, in which he wore a black baseball cap and khaki trousers.
"I don't have a single American friend. I don't understand them," he was quoted as saying in a photo package that appeared in a Boston University student magazine in 2010.
He identified himself as a Muslim and said he did not drink or smoke. He said he hoped to fight for the US Olympic team and become a naturalised American. He said he was studying at Bunker Hill Community College to become an engineer.
Dzhokhar, 19, attended the prestigious Cambridge Rindge and Latin school, participating on the wrestling team. In May 2011, while in his final year at high school, he was awarded a US$2,500 scholarship from the city to pursue higher education.
He attended the University of Massachusetts at Dartmouth, university officials said yesterday as the campus was evacuated. The university would not say what he was studying. The father of the suspects, Anzor Tsaraev, said however that his younger son was a second-year medical student.
"My son is a true angel ...," he said by telephone from the Russian city of Makhachkala. "He is such an intelligent boy. We expected him to come on holidays here."
He added: "They were set up, they were set up! I saw it on television; they killed my older son Tamerlan." He ended the call angrily, saying: "Leave me alone, my son's been killed."
Those who knew the brothers are stunned. A host of a Boston-based public radio programme, Robin Young, posted on Twitter a photo of her nephew with Dzhokhar Tsarnaev, their arms around each other, at their graduation.
"Heartbreaking pic," Young wrote.
Tim Kelleher, a wrestling coach for a Boston school that competed in 2010 against Dzhokhar's team, said the young man was a good wrestler and that he'd never heard him express any political opinions.
"He was a tough, solid kid, just quiet," Kelleher said.
A high school classmate, Eric Machado, told CNN that Dzhokhar showed no "tell-tale signs of malicious behaviour". He said: "We partied. We hung out. We were good high school friends."
Machado recalled Dzhokhar once said something in conversation about terrorism, but there was "no evidence that would lead any of us to believe that he would be capable of this."
Additional reporting by The Guardian, Reuters