Salman Abedi was born to Libyan parents and grew up in a devoutly Muslim family in Manchester, family friends and neighbours say.
His two brothers and father have been taken into custody in Britain and Libya as investigators try to uncover what is believed to be a network of terror behind the Monday bombing fronted by Salman.
Here is what we know about the Abedis.
SALMAN ABEDI, 22
Acquaintances were stunned to learn that Salman had carried out the suicide bombing but there were signs that he was troubled, friends and officials say.
He was born in Britain to parents who had fled Libya during the four-decade dictatorship of Muammar Gaddafi.
In the Libyan-British community in southern Manchester where Salman lived, he was known as a university dropout, an "awkward" young man and an "isolated, dark figure" who talked to few people and travelled back and forth between Britain and Libya.
But members of the Libyan immigrant community reported to the local authorities that they feared Salman was turning increasingly radical, two friends of the family said. The British security authorities have acknowledged they were aware of Salman, but said he was not considered a major terrorism risk.
When his parents moved back to Libya a few years ago after Gaddafi was deposed, Salman and his brothers stayed behind in Manchester.
HASHEM ABEDI, 20, BROTHER
Salman was not the only one in his family who caused concern in Manchester. His 20-year-old brother, Hashem, was arrested in Libya on Tuesday night by the Special Deterrence Force.
Officials said he told the authorities that he had been involved in planning the Manchester attack.
A family friend said Salman and Hashem had changed after another youth - an 18-year-old Manchester resident also of Libyan descent - was killed in the northern British city a year ago.
That teenager, Abdulwahab Hafidah, was stabbed in the neck in what local media reports called retaliation for his having gone into rival gang territory. Hashem appeared to have known Hafidah.
"It became a big source of anger for the youngsters in the Libyan community. Salman and Hashem saw it as an act of anti-Muslim hate crime; they called him a martyr," the family friend said.
In a Facebook post, the Special Deterrence Force, which operates out of a former US military base, said Hashem had been a member of the Islamic State in Iraq and Syria.
ISMAIL ABEDI, 23, BROTHER
The oldest of the four Abedi children, Ismail has also been taken into custody since the attacks. He is known to have volunteered at the Manchester Islamic Centre, the local mosque also known as Didsbury mosque.
RAMADAN ABEDI, FATHER
Better known as Abu Ismail to the Libyan community in Manchester, Ramadan worked as an odd-job man in the city and has been working for the Libyan police force in recent years, according to an official.
He was detained by a Libyan militia yesterday. A Libyan security source said Ramadan was once part of the Libyan Islamic Fighting Group, a militant organisation with alleged ties to Al-Qaeda.
Ramadan is a well-known figure within the Libyan community in Manchester, said a member of the community. He sometimes led the call to prayer at the Manchester Islamic Centre, which Ramadan and his children attended. Besides the three boys, he also has a daughter called Jomana.
WASHINGTON POST, REUTERS, NYTIMES