Last week, we brought you news that Lena Headey (Game of Thrones, Sarah Connor Chronicles) and Jared Harris (Mad Men, Sherlock Holmes: A Game of Shadows) have been cast in the big screen adaptation of Cassandra Clare‘s New York Times best-selling YA series, The Mortal Instruments: City of Bones.

According to JustJared, Kevin Zegers (Titanic: Blood and Steel, Gossip Girl) has been cast as Alec Lightwood, “the gay brother of Isabelle (Jemima West)” who is jealous of Jace’s (Jamie Campbell Bower) feelings for the main character Clary (Lily Collins).

Author Cassandra Clare has been very vocal about her thoughts on previous casting announcements thus far and has not confirmed this news as of yet.

Synopsis for City of Bones, the first book of The Mortal Instruments series:

City of Bones begins with a sixteen-year old girl named Clary Fray (Lily Collins,) who lives in New York with her mother, an artist. She comes home one night to find her apartment ransacked, her mother gone — and a slavering demon ready to tear off her head. Once the demon’s dealt with, Clary follows the clues to her mother’s disappearance into an alternate New York filled with hideous demons, hard-partying warlocks, not-what-they-seem vampires, an army of werewolves and the scariest thing of all: the secrets of her mother’s past. She also finds herself torn between two boys — her best friend Simon, for whom she’s developing new feelings, and the mysterious demon hunter Jace, who has a past more tangled than her own. She becomes a part of the secret word of the demon hunters, or Nephilim, and as she does discovers she might be more connected to them than she originally thought.

The Mortal Instruments is slated to hit theaters August 23, 2013.