He was a descendant of the Kantakouzenoi that settled in Serbia after the marriage between Despot Đurađ Branković and Irene Kantakouzene. His father was most likely one of the Kantakouzenoi that settled Serbia after the marriage of Serbian Despot Đurađ Branković (r 1427–1456) and Irene Kantakouzene in 1414.
Janja"s father, whose name is unknown, was a customs officer (gabelotto) at Novo Brdo during the 1440s. In Ragusan documents dated to 1461 and 1462, Janja is mentioned as "Jagno Catacusini de Novo Brdo". The presence of Demetrius and Janja in Novo Brdo after 1467 shows that the Kantakouzenoi were not affected by Mehmed II"s massive deportation and forced settlement of the inhabitants to Istanbul, which happened that year.
He later rented the silver mines of Novo Brdo.
A Palaiologos buried their remains in Galata on 16 September the same year. The reason for his family"s execution is not known.
Matei Cazacu made the assumption that Janja was a relative to Mahmud Pasha"s mother. According to Stavrides it is not impossible that Janja"s business with the Ottomans were due to his relations to a high-standing official, such as Mahmud Pasha.
Babinger mentioned that Janja was a close relative of Catherine of Cilli, the daughter of Đurađ Branković and Irene Kantakouzene.
Irene"s brother George was allegedly a cousin of Mahmud Pasha"s mother.
