Disambiguation: Guardian; Hornblower; Herald; Vox
First published in: 1970
Mal Duncan first appeared in Teen Titans (DC, 1966 series) #26 (March-April 1970). He became the Guardian in issue #44 (November 1976). He became Hornblower in issue #45 (December 1976). He returned as the Guardian in issue #49 (August 1977). It was revealed in Tales of the Teen Titans (1984 series) #50 (February 1985) that Mal and Karen Beecher (Bumblebee) had gotten married. In Post-Crisis continuity, Mal Duncan became Herald instead of Hornblower, as seen in Secret Origins Annual (DC, 1987 series) #3 ([May] 1989). He first appeared as Vox, unnamed, in Teen Titans (DC, 2003 series) #35 (June 2006); named in issue #36 (July 2006).
Link: https://en.wikipedia.org/wiki/Mal_Duncan