Georgios, his father Chrysanthos and his three brothers, who died young, were all physicians.

In 1821, as the Ottoman authorities suspected the Greeks of planning a revolution, he was requested to come to Tripolitsa along with other primates; at the suggestion of Germanos of Old Patras, he feigned illness and did not attend.

He provided the Greek troops in the Peloponnese with provisions, and distinguished himself in the battles of Patras, Lala and of Chlemoutsi.

In early 1825, during the Greek civil wars of 1824–1825 he and his son Chrysanthos Sisinis were arrested and imprisoned in Hydra.

Under Governor Ioannis Kapodistrias, he was appointed a member of the Panellinion, and in 1829 he was named president of its successor, the Senate.