Two of the men blew themselves up at the Brussels' airport, a third inside a metro train, killing 31 people and injuring 300 on March 22.
A fourth suspect was charged Saturday with terrorist murder and identified by the federal prosecutor's office only as Faycal C.
A fifth man remains on the run.
Here are brief profiles of the five:
Faycal C, or Faycal Cheffou
Faycal C, believed to be the "man in a hat" pictured in CCTV footage alongside the two airport bombers, but whose device did not go off, is the first person to face terrorist offences over the bloodiest attacks ever to strike the symbolic capital of Europe.
Sources close to the inquiry told AFP he was Faycal Cheffou, an independent journalist who was accused by the Brussels mayor last year of trying to recruit jihadists among refugees and who can be seen on YouTube in 2014 demanding the authorities respect the rights of asylum-seekers.
He was arrested late Thursday close to the federal prosecutor's office with two others when tailed by police, and "has been charged with taking part in a terrorist group, terrorist murder and attempted terrorist murder."
Police searched his home but found no explosives or weapons.
Najim Laachraoui
Moroccan-born Najim Laachraoui, 24, has been identified as one of the two airport suicide bombers and is believed to have been the bomb-maker for November's attacks in Paris.
He is described as having been a good student with a good disciplinary record, and friends and family remember an easy-going youngster who liked playing frisbee and football.
In 2012 he enrolled for a first year electro-mechanical engineering course at Brussels Free University (ULB) but failed to sign up for a second year.
He was a practising Muslim, whose radicalisation shocked the family. When he told them in 2013 he was heading to Syria they contacted the police.
He resurfaced in September, two months before the Paris attacks, when he was stopped by police on the Austria-Hungary border. He was travelling with Paris attacks suspect Salah Abdeslam and using the false identity of Soufiane Kayal.
Investigators have found traces of Laachraoui's DNA on explosives used in the Paris gun and suicide bomb assaults, as well as at hideouts and a suspected bomb factory in the Schaarbeek district of Brussels.
Ibrahim El Bakraoui
The 29-year-old was one of the two airport suicide bombers and is the brother of Khalid, who blew himself up on a train at Maalbeek metro station in the Belgian capital.
Long before, the two lived the lives of small-time Brussels hoodlums, piling up convictions for carjackings, robberies and shoot-outs with police.
Baby-faced Ibrahim was handed a nine-year sentence in 2010 after a gunfight with police. He took part in a bungled robbery at a Western Union office in which an officer was shot and wounded.
After his release from prison in 2014 he went to join the Islamic State (IS) group in Syria or Iraq.
Turkey said it had detained Ibrahim in June last year as a "foreign terrorist fighter" and then deported him to the Netherlands, but that Belgium failed to confirm his links to terrorism.
Ibrahim, who is seen on the CCTV footage with two others pushing airport trolleys with their bomb-laden bags, left a confused and scared message on an abandoned computer, according to the Belgian federal prosecutor.
"Hunted everywhere... no longer safe," Ibrahim said in the message. "I don't know what to do."
Khalid El Bakraoui
His younger brother Khalid, 27, who blew himself up at Maalbeek station just a short walk from the main EU institutions, was a convicted carjacker, receiving a five-year sentence in 2011.
On an Interpol "terrorism" list, Khalid is suspected of having rented a flat under a false identity in the Forest district of Brussels that was raided by police on March 15.
It was as a hideout months earlier for the Paris team and he was thought to have rented other properties used to prepare the Paris attacks, including one in the southern Belgian city of Charleroi from where ringleader Abdelhamid Abaaoud set off to spearhead the assault.
The fifth man
A man caught on CCTV footage at the metro station talking to the train bomber remains on the run.
