John returned to Trebizond in early 1429 and seized the throne, killing Alexios and forcing Alexander into exile.
While in exile, Alexander lived in Constantinople, as his sister Maria had married the Byzantine emperor John VIII Palaiologos.
Alexander attempted to gain Byzantine and Genoese support in organizing an expedition to depose John and take the Trapezuntine throne for himself, but had little success.
Perhaps John was motivated by the fact that he lacked sons of his own and distrusted their only other brother, David, to invite Alexander back and designate him as heir and co-emperor c. 1451.
George Finlay suggested in 1851 that Alexander was called Skantarios by his contemporaries and that this indicated Turkish influence in the Greek dialect of Trebizond.
[4] Certain modern scholars, such as Michel Kuršanskis,[3] as well as the Prosopographisches Lexikon der Palaiologenzeit, favor using the name Skantarios rather than Alexander.
[5] As the eldest son, Alexios had initially made Alexander's brother John the designated heir, and possibly associated him with imperial power as co-emperor.
The familial issues reached a breaking point c. 1426, when John discovered that his mother (Alexios's wife) Theodora Kantakouzene was having an affair with the treasurer.
[10] Alexander is next attested in 1451, a turbulent year in Trebizond as relations had deteriorated between John and the Genoese, with David even having been sent on naval expeditions against them.
Surprisingly, Alexander is recorded to have lived in Trebizond at this time, together with his wife Maria and their young son, Alexios.