Constantine III of Byzantium
Heraclius Constantine, or Constantine III, was the eldest son of Heraclius. He was also the older half-brother of Heraclonas, who was the son of Heraclius' second wife Martina. For political reasons Heraclius considered Martina to be mother of them both. Constantine became emperor when Heraclius died in 641, and during his reign the Arabs conquered Egypt. He died of tuberculosis after only four months, leaving Heraclonas sole emperor; it was rumoured, however, that Martina had him poisoned, which led to instability during Heraclonas' reign.