Alexander (Alec) Lightwood is the eldest of Maryse and Robert Lightwood’s 3 children. He is also Jace Herondale (Lightwood)’s parabatai.
Alec is described as having jet black hair and bottle blue eyes and he is taller than Jace. Alec takes an instant disliking to Clary, as he finds it difficult to trust her, referring to her often as ‘mundane’ even after it is revealed Clary is also a Shadowhunter. It is also obvious that Alec is jealous of Clary as her and Jace’s relationship develops.
Alec Lightwood is played by Kevin Zegers in the film.
Alec, being the oldest, often tells Isabelle and Jace off for going into things head first. He has never killed a demon at the start of City of Bones, because he often protects Isabelle and Jace. He is also jealous of Clary. Clary however, confronts him on this, asking him if he is gay and loves Jace. Alec is mad at Clary for speaking about him in such way, and tells her not to tell Jace anything. When the group attend Magnus Bane’s party, he and Alec meet, and at some point begin secretly seeing each other. They later fall for each other and Alec begins to accept Clary as a Shadowhunter.