In 608, Heraclius the Elder renounced his loyalty to the Emperor Phocas, who had overthrown Maurice six years earlier. The rebels issued coins showing both Heraclii dressed as consuls, though neither of them explicitly claimed the imperial title at this time. Heraclius’s younger cousin Nicetas launched an overland invasion of Egypt; by 609, he had defeated Phocas’s general Bonosus and secured the province. Meanwhile, the younger Heraclius sailed eastward with another force via Sicily and Cyprus.
As he approached Constantinople, he made contact with prominent leaders and planned an attack to overthrow aristocrats in the city, and soon arranged a ceremony where he was crowned and acclaimed as Emperor. When he reached the capital, the Excubitors, an elite Imperial Guard unit led by Phocas’s son-in-law Priscus, deserted to Heraclius, and he entered the city without serious resistance. When Heraclius captured Phocas, he asked him “Is this how you have ruled, wretch?” Phocas’s reply—”And will you rule better?”— Heraclius was so enraged that he beheaded Phocas on the spot. He later had the genitalia removed from the body because Phocas had raped the wife of Photius, a powerful politician in the city.
On October 5, 610, Heraclius was crowned for a second time, this time in the Chapel of St. Stephen within the Great Palace; at the same time he married Fabia, who took the name Eudokia. After her death in 612, he married his niece Martina in 613; this second marriage was considered incestuous and was very unpopular. In the reign of Heraclius’s two sons, the divisive Martina was to become the center of power and political intrigue. Despite widespread hatred for Martina in Constantinople, Heraclius took her on campaigns with him and refused attempts by Patriarch Sergius to prevent and later dissolve the marriage.
Constantine was crowned co-emperor by his father on 22 January 613 and shortly after was betrothed to his cousin, Gregoria, a daughter of his father’s first cousin, Nicetas. As the couple were second cousins, the marriage was, again, technically incestuous, but this consideration must have been outweighed by the advantages of the match to the family as a whole. Furthermore, its illegality paled into insignificance beside Heraclius’ marriage to his niece Martina the same year. In comparison, Constantine’s marriage was far less scandalous.
Constantine and Gregoria married in 629 or perhaps early 630 and in that year their first child, Constans II was born. Their second child was another son, Theodosius. They also had a daughter named Manyanh who later married the last Sassanid King of Persia, Yazdgerd III.
Constantine became senior Emperor when his father died in 641. He reigned together with his younger half-brother Heraklonas, the son of Martina. His supporters feared action against him on the part of Martina and Heraklonas, and the treasurer Philagrius advised him to write to the army, informing them that he was dying and asking for their assistance in protecting the rights of his children. He also sent a vast sum of money, more than two million solidi, to Valentinus, an adjutant of Philagrius, to distribute to the soldiers to persuade them to secure the succession for his sons after his death. Indeed, he died of tuberculosis after only four months, leaving Heraklonas sole emperor. A rumor that Martina had him poisoned led first to the imposition of Constans II as co-emperor and then to the deposition, mutilation, and banishment of Martina and her sons.