Konstantinos 29's name was originally Symbates (Symbatios) and he received the name Konstantinos in 814 when he was crowned emperor: Scriptor Incertus 346 (cited below), Theoph. Cont. II 1 (p. 41) (Συμβατίῳ τῷ κατὰ στέψιμον μετονομασθέντι Κωνσταντίνῳ), Zon. XV 22. 2 (Σαββάτιος, ὃς ἐν τῷ ἀναγορεύεσθαι μετωνόμαστο Κωνσταντῖνος), Genesius I 21. Son of Leo V (Leo 15) and Theodosia 1, brother of Basilios 54, Gregorios 70 and Theodosios 39: Theoph. Cont. II 1 (p. 41), Genesius I 21, Zon. XV 22. 2. Son of the emperor Leo 15; still a child (μικρὸν ὄντα), at Easter 814 (16 April) he was crowned by his father and his name was then changed to Konstantinos (καὶ ἐπονομαζόμενον Συμβάτην ἐψεύσατο λέγων ὅτι Κωνσταντῖνος καλεῖται); the two were then acclaimed as Leo and Constantine, thus recalling the acclamations of the iconoclasts Leo III (Leo 3) and Constantine V (Konstantinos 7): Scriptor Incertus 346.

Present at the iconoclast Council called by his father after Easter 815: Scriptor Incertus 360 (Συμβάτιον τὸν υἱὸν αὐτοῦ, ὃν ἐπέθηκεν Κωνσταντῖνον). After the murder of Leo 15 in 820, his children were tonsured, castrated and forced to become monks on the island of Prote: Theoph. Cont. II 1 (p. 41), Leo Gramm. 211, Genesius I 21, Zon. XV 22. 2, cf. Nicetas, Vita Ignatii 493B (they were castrated and tonsured - τούς τε αὐτοῦ υἱοὺς εὐνουχισθῆναι καὶ καρῆναι). After castration Konstantinos 29 allegedly lost his voice and only regained it after praying to St Gregory Theologos and venerating his icon; he and his brothers and their mother were allowed to live on the revenues from some of their estates and they were allowed to have attendants: Zon. XV 22. 3-7.

(Publishable link for this person: )