Christophoros 1 was the son of the emperor Constantine V (Konstantinos 7) and his third wife Eudokia 1, brother of Nikephoros 5; on 2 April 769 (Easter Sunday; indiction 7) he was crowned kaisar (καίσαρας) together with his brother: Theoph. AM 6260, Nic. Brev. de Boor 77, Mango 87, Zon. XV 8.2 (ἐκ δὲ τῶν ἄλλων Χριστοφόρον, Νικηφόρον τε καὶ Νικήταν. καὶ τοὺς μὲν δύο Καίσαρας ἔστεψε). They were the two eldest sons of Konstantinos 7 by Eudokia 1 (τοὺς ἐξ αὐτῆς δύο υἱοὺς αὐτοῦ, Χριστοφόρον καὶ Νικηφόρον): Theoph. AM 6260. They were born between 753 (death of Maria 1) and 763 (birth of their younger brother Niketas 5). Christophoros 1 was also brother or half-brother of the emperor Leo IV (Leo 4), Niketas 5 and Anthimos 1: Nic. Brev. de Boor 64, Mango 69; de Boor 70, Mango 78; de Boor 76, Mango 86. Brother also of Eudokimos 1 (who is described as the brother of the emperor Leo IV (Leo 4) - τὸν ἀδελφὸν αὐτοῦ): Theoph. AM 6268.

Christophoros 1 took part in the ceremonies of 13 and 14 April 776, surrounding the coronation by Leo IV (Leo 4) of Constantine VI (Konstantinos 8) (καὶ προῆλθεν ὁ βασιλεὺς σὺν τοῖς δυσὶ καίσαρσι καὶ τρισὶ νοβελισίμοις καὶ τῷ νέῳ Κωνσταντίνῳ εἰς τὴν μεγάλην ἐκκλησίαν), but he was perhaps implicated with Nikephoros 5 in May 776 in a conspiracy against Leo IV (Leo 4) and exiled like Nikephoros 5: Theoph. AM 6268 (NB This source names Nikephoros only, but alludes to the crowds demanding the exile of both men (τοῦ παρασταλῆναι ἀμφοτέρους ἐκ τοῦ μέσου); this probably means the two kaisars, but see Theoph. AM 6268, trans. Mango and Scott, p. 622, n. 9 for a different reading.

Early in the reign of Constantine VI (Konstantinos 8), after a conspiracy to put Nikephoros 5 on the throne was discovered, Christophoros 1 and his brothers were tonsured, consecrated priests and made to perform religious ceremonies at Christmas: Zon. XV 10.4 (τοὺς δὲ τοῦ ἀνδρὸς αὐτῆς ἀδελφοὺς τούς τε Καίσαρας καὶ τοὺς νωβελισίμους καρῆναι παρασκευάσασα καὶ ἱερωσύνης ἀξιωθῆναι καὶ μεταδοῦναι τῷ λαῷ τῶν ἁγιασμάτων ἐποίησε κατὰ ἑορτὴν τῆς τοῦ σωτῆρος γεννήσεως). When the tagmata tried to overthrow Constantine VI (Konstantinos 8) in 792 and install Nikephoros 5 as emperor, Constantine VI (Konstantinos 8) had Nikephoros 5 blinded and cut off the tongues of Christophoros 1, Niketas 5, Anthimos 1 and Eudokimos 1; the date was August 792: Theoph. AM 6284 (the allusion to both the sons of the emperor Constantine V (Konstantinos 7) here probably refers to the two eldest, Nikephoros 5 and Christophoros 1; there were five sons in all), cf. Zon. XV 12. 12 (tongue cut out after the conspiracy was detected). They apparently lived in the palace of Therapia in 797, when they were involved in a conspiracy against the empress Eirene 1; it was discovered and they were sent to Athens into exile: Theoph. AM 6290, Zon. XV 13.18-19.

After the failure in 799 of another conspiracy involving them they were all blinded on the orders of Eirene 1: Theoph. AM 6291, Zon. XV 13.20-21. In 812 the brothers were alive under guard on the island of Panormos; following another conspiracy they were exiled to Aphousia (in the sea of Marmara) (see further Nikephoros 5): Theoph. AM 6304. See also Rochow, Konstantin V, pp.211-12.

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