Demetri

Demetri is a member of the Volturi Guard, a vampire, an honorary member of the Seely Court, and the husband of Lyra.

Crimson Twilight
In Crimson Twilight, Demetri first meets Lyra, and begins to have an interest in her. During the process of courting her, he gets pulled into a whirl-wind of events, causing him to get married, change his wife into a vampire, and help run the Seely Court.