7th century icon, originally from the Monastery of St. Catherine on Mt. Sinai, now in the Kiev Museum of Eastern and Western Art, here from the cover of John Boswell's Same-Sex Unions in Premodern Europe (New York: Villard, 1994). Christ is shown in the traditional Roman position of pronubus (best man) overseeing the wedding.
Serge and Bacchus were Christian lovers martyred in the early 4th century. See Boswell, who has an account of their lives (pp. 146-61) and a translation of a Greek vita (pp. 375-90).