Declan Robertson, 17, and Andrew Parfinowski, 18, both of Edinburgh, were convicted by a jury last month of murdering Brett Lodge, 17, by punching, kicking and striking him with a baseball bat.
A judge told them that a life term was mandatory for murder, and he also had to fix the minimum period they would be detained.
John Morris, QC, said: “The punishment part is the period which must be served before you are eligible for parole. This is very important: it does not mean you will be released at the conclusion of that period. When you are released will remain a matter for the parole board.
“Nor is it designed in any way to compensate the family (of Brett Lodge) for the devastation they have obviously suffered from his death. No sentence I could possibly pass can do that. You were both best friends of the deceased which makes this an utter tragedy. I take account of your age, and you both seem to have shown some genuine remorse. But the taking of a life demands that a substantial period is imposed...13 years.”
A third youth, Cameron McKail, 17, also of Edinburgh, who was found guilty of a reduced charge of assaulting Mr Lodge was put under supervision for a year.
Judge Morris said it was a relatively minor assault, and McKail had had a murder charge hanging over him.
The High Court in Edinburgh heard that all three had known Mr Lodge most of their lives and regarded him as a friend.
The attack took place on 1 July last year, after a party in a house in the Liberton area of the city where teenage revellers drank alcohol and smoked cannabis.
An argument broke out and Mr Lodge was assaulted on a path nearby and sustained serious head injuries. He died in hospital eight days later.
Following the trial, his mother, Gillian Lodge, said: “Brett was a happy boy with a cheeky sense of humour, who was kind, caring, and did his best to help others and cheer people up. He spent a great deal of time with his family, and was very popular with his friends. Losing Brett in this way has been horrendous for our family, and has left a big hole in our hearts. It is still hard to believe he has gone, and harder still to know that his life was taken by people he trusted, and thought of as friends.”
Herbert Kerrigan, QC, for Robertson, said he had been only 16 at the time of the offence. The jury had accepted the attack occurred “in hot blood” and, in one sense, added Mr Kerrigan, it was explicable by Robertson’s lack of experience of life.
“It is clear the intervention of Parfinowski ended a period of argument and brought in a situation of melee. Robertson has consistently accepted his response was entirely inappropriate and it resulted in the severe injury and subsequent death of his friend. This incident will undoubtedly haunt him for the rest of his days,” said Mr Kerrigan.
Brian Gilfedder, for Parfinowski, said he was also 16 at the time and had no record.
“He clearly has shown remorse. I don’t think anybody expected the tragic outcome at the time of the incident,” said Mr Gilfedder.
Robbie Burnett, for McKail, said he was of good character, and was to receive a meritorious award from the police for going to the aid of a man attempting to jump from North Bridge, Edinburgh, in March this year.
Mr Burnett quoted from a letter from the chief constable of Lothian and Borders Police: “Your initiative was both courageous and praiseworthy and your prompt and effective actions surely prevented a much more serious incident occurring.”