Kantakouzenos' son Matthew has fought on for a few years following his father's abdication, but the dynasty of Kantakouzenos will not be perpetuated.

From his Thracian domain, centered on Gratzianous, a well-fortified town named for the Roman emperor Gratian, has led several wars against the Serbs.

An attack, which he had prepared in 1350, had been frustrated by the defection of his Turkish auxiliaries.

However with five thousand Turks he had tried to reestablish his former appanage along the Serbian-Byzantine border by attacking this region but had failed to take Serres and soon is defeated in battle in late 1356 or early 1357 by a Serb army under Vojvoda Vojihna, the holder of Drama, a major fortress in the vicinity.

The Serbs capture Matthew with the intention of releasing him when he has raised the large ransom they demand.

However John V Palaiologos, who has rapidly moved in to occupy Matthew's lands, offers Vojihna an even larger sum to turn Matthew over to him.

In exchange for the Despotate of the Morea, Matthew surrenders Gratzianous and all his Thracian domains to John V.