Aamir Siddiqi was attacked at his home in Wales by Jason Richards, 38, and Ben Hope, 39, in April 2010.
The killers, who will be sentenced next Friday, had been paid 1,000 pounds each to murder a different man on a neighbouring street in Roath, Cardiff.
During a trial which ended yesterday, a Swansea Crown Court jury was told the hitmen had been guilty not just of murder but "staggering incompetence".
A third man who is still wanted in connection with the investigation is waiting to be extradited from India.
The Dubai-born fugitive, who prosecutors here believe ordered the attack and fled Britain, was arrested in Hyderabad with a fake Indian passport in November 2011 and the authorities are working on his extradition documents.
Police believe the real target was a man called Mohammed Tanhai.
He had become embroiled in a dispute with the fugitive businessman, who cannot be named for legal reasons, over a failed house sale, the prosecution said.
Outside court, Aamir's family spoke of the moment the pair of drug addicts had barged into their home.
The victim's father Iqbal, 68, and mother Parveen, 55, were also injured as they came to his aid and tried to fight off the masked assassins.
As he was expecting his Quran teacher to call, Aamir opened the door of his parents' home but within seconds the masked men started attacking him with a knife.
They said nothing during the attack but the court heard how they made strange "howling noises".
"Aamir was a beautiful person with a bright future. If he was still with us he would be looking forward to turning 21 this year and completing his law degree.
"We are pleased today that justice has finally been done and we can finally start to deal with the reality of losing Aamir," his sister Umbareen said, reading out a statement from her family.
South Wales Police searched through large amounts of CCTV footage as part of the murder investigation.
"Despite being left totally devastated at losing their beloved son and brother in such tragic circumstances, Aamir's loving family have shown tireless strength and remarkable dignity throughout this ordeal.
"The investigation team was overwhelmed not only by their support but also that of the community who came forward with information and played an invaluable role during such as complex inquiry," said Detective Superintendent Paul Hurley.
London: Two contract killers have been found guilty of stabbing to death a 17-year-old British Asian student in a case of mistaken identity nearly three years back.
First Published: Saturday, February 02, 2013, 20:16