Kika, Braithwaite and Alleyne each denied being the knifeman
Three men have been given life sentences for murdering 16-year-old Ben Kinsella in north London.
Ben, the brother of EastEnders actress Brooke Kinsella, was stabbed 11 times as he fled from a fight in Islington.
Michael Alleyne, 18, Juress Kika, 19, and Jade Braithwaite, 20, all from London, were all ordered to serve a minimum of 19 years in prison.
After the sentencing, Ben's sister said: "It's little more than Ben lived, so it is not really enough."
The trial heard Ben was running away from the fight in a bar when he was attacked on 29 June last year.
The family of Ben Kinsella applauded outside court at the sentences
The Old Bailey heard he was stabbed in revenge for a claim that Braithwaite had earlier been "disrespected".
Sentencing, the Common Serjeant of London, Judge Brian Barker, told the defendants: "Your behaviour generates outrage in all right-minded people and your blind and heartless anger defies belief.
"He had in front of him a lifetime of promise.
"You have taken all that away from him in a brutal, cowardly and totally unjustified attack."
The judge said the crime was aggravated by the fact that they picked on "an obviously younger and smaller lone victim", the judge added.
"His family will never get over it but he will never be forgotten."
The trial had heard that although the confrontation in the bar had nothing to do with him, Ben was chased along the street with other youngsters - and was stabbed to death when he stopped running.
The defendants had admitted punching him but each denied being responsible for stabbing Ben, who had been celebrating the end of his GCSE exams at the time.
Lawyers for the defendants told the judge the three killers had been served with letters from the prison authorities following fears of retaliation.
The letters, asking inmates to discuss any fears or incidents, are given to prisoners who are likely to be targets of retribution.
Prisoners with fears could be placed in solitary confinement for their own safety.
Nerida Harford-Bell, defending Braithwaite, said: "Jade Braithwaite understands he is a marked man."
Ben's murder came in a year when 28 teenagers died in violent circumstances.
Linda Robson, a close friend of the Kinsellas, reacts to the sentences
About 400 people joined Ben's family to march against knife crime following his death.
After the verdicts on Thursday, Ben's father George, 49, said: "How many more families will have to stand outside the Old Bailey to get justice for their child?
"Our son's only crime was to be the last one, running away, from those animals.
"Knife crime is now sadly embedded in the very heart of Great Britain. Parents live in fear until their children are safely home."
After the verdicts, it emerged Kika had been on the run from police following a robbery in which a man was stabbed nine days before Ben's death.
Alleyne was being supervised by the local youth offending team as part of an 18-month detention and training order for drug dealing.
He had been released three months earlier after serving half the sentence in a detention centre.