[4][5] Varzos also considers Manuel a brother of the protospatharios Nikephoros Komnenos, who was named governor of the Armenian region of Vaspurakan soon after its annexation in 1021, but although possible, such a relationship cannot be proven.

[2][4][6] Manuel is mentioned for the first time in 978, when he led the defence of Nicaea against the rebel general Bardas Skleros, who had risen up against Emperor Basil II (r. 976–1025).

Although his great-granddaughter, the princess Anna Komnene, claims in her Alexiad that he had been named strategos autokrator (commander-in-chief) of the East and sent with full powers to deal with the revolt, it is far more likely that he was merely a local commander.

At that point Manuel was able to fool Skleros, by pretending that he had mountains of wheat and was considering joining him, into allowing him and the inhabitants to depart freely for Constantinople.

[2] Manuel owned lands in Kastamon, on the Black Sea coast of north-central Anatolia, inherited after his death by his eldest son,[2] and which became the stronghold of the family in the 11th century.