Constantine III

Herakleios Constantine, known in subsequent historiography as Constantine III, reigned as Byzantine Emperor for four months in 641. He'd previously reigned as co-emperor with his father, Herakleios, beginning in 613. Constantine himself reigned with his half-brother, Heraklonas, whom Herakleios had fathered by his second wife, Martina. Constantine was in poor health, and various factions began plotting in expectation that he was dying.

Constantine succumbed to tuberculosis four months after becoming senior emperor. Heraklonas reigned for a months himself. Rumors that Constantine been murdered by Martina lead to first the ascension of Constans II as co-emperor, and then the ouster of Heraklonas and Martina. Heraklonas' nose was removed, and Martina's tongue was cut.

Constantine III in Justinian
In his memoir, Justinian II summarized Herakleios Constantine's short reign, and prayed that God had mercy on his great-grandfather's soul.