"It was my brother who killed Meredith on the night of November 1, 2007. Amanda, Raffaele (Sollecito) and (Rudy) Guede are innocent," Luciano Aviello, 41, told Knox's lawyers in March, according to Oggi.
Aviello, who spent 17 years in jail for crimes and ties with the Naples-area Camorra crime syndicate, spoke to Knox's lawyers after the court refused to hear him for three times, judging him unreliable.
Knox, now 22, was sentenced to 26 years in prison for murdering her former roommate Kercher, a British student, in a drug-fueled sex game that turned violent. She has appealed the conviction.
Knox's then boyfriend, Italian student Sollecito and an Ivorian man, Guede, were also convicted of the murder.
"My brother confessed the murder to me and gave me the blood-stained knife and a set of keys (to hide)," Aviello said, adding that he would help investigators find these items, if the court in the central Italian town of Perugia decided to hear him.
Knox's lawyers have asked the court to hear Aviello in the appeal trial.
Since beginning to collaborate with Italian justice, some of Aviello's allegations have proved unreliable, Oggi reported.
Kercher was found November 2, 2007, in a pool of blood under a duvet with multiple stab wounds to the neck in her room in the cottage she shared with Knox.
According to Aviello's reconstruction, his brother Antonio and an Albanian man killed Kercher in a botched burglary attempt.
The two, looking to steal paintings, ended up in Kercher's house where the British student found them and began screaming. Antonio Aviello tried blocking her and then stabbed her.
Aviello and the Albanian man would have then found Ivorian Rudy Guede in the bathroom of the house and intimidated him into silence.