Career
Sisinnios first appears in Irene"s unique triumphal procession on Easter Monday, 1 April 799, through the imperial capital, Constantinople. At the time, he held the post of strategos (military governor) of Thrace, the theme closest to Constantinople, and holder of the supreme dignity of patrikios. He was one of the four patrikioi (along with Bardanes Tourkos, Constantine Boilas, and Sisinnios" brother Niketas) leading the four white horses which drew the imperial carriage, a role which marked these men out as the most prominent of Irene"s supporters among the high dignitaries of the state.
They were thus among the leaders of her overthrow by the General Logothete, Nikephoros I, on 31 October 802.
As a patrikios, Sisinnios remained influential under Nikephoros, but is not recorded as having held any specific post. Sisinnios was among the magnates who accompanied Nikephoros on his campaign against the Bulgars in spring-summer 811, and was among those slain in the disastrous Battle of Pliska on 26 July.
