Jason is Alison's brother and Spencer and Melissa's half-brother.
He had an interesting relationship with his late sister; though they often
fought, they were both conniving and willing to keep each other's secrets.
Jason attended high school and was friends with Ian and Garrett, and they
formed a club called N.A.T. He revealed to Spencer that Alison blamed the
accident where Jenna was blinded on her, though Spencer believes Jason knows
this to be a lie. After Ian's death, Jason returns to Rosewood, moving back
into his old house and papering up the windows, apparently looking for
something that Alison hid. He explains to Aria, that he can't remember what he
was doing on the night of Alison's murder and that someone sent him a note
afterward with 'I know what you did', written on them causing him to
fear he might have killed Alison. We later find out that Spencer's father had
had an affair with Jason's mother.
Garrett is a police officer investigating the case of Alison
DiLaurentis' death, who is initially assigned to trail Spencer, a suspect in
Alison's death. Although he appears to be sympathetic towards the girls, in
reality he is secretly dating and in an alliance with Jenna. He was a member of
N.A.T along with Jason and Ian, who he went to high school with. Garrett and
Jenna have broken up. Aria and Spencer see Garrett watching them after they
talk to the guy who Alison owed money to prior to her murder. Garrett then gets
arrested, for Alison's murder in front of Melissa. Later in season 3 Garrett is
willing to tell Spencer everything he knows and tells her he will leave town
right after. As he begins to tell her they get interrupted. Aria is then seen
trapped in a box, next to her you see Garrett's body.
Ian is Melissa's late husband. He attended high school with
Jason and Garrett and was part of their N.A.T. club. Ian dated Melissa prior to
Alison's death, although he was secretly carrying on an affair with Alison, he
also flirted and tried it on with Spencer, who had a crush on him. He returned
to Rosewood shortly after Melissa broke off her engagement with Wren. He had an
uneasy relationship with Spencer, who became suspicious of him and believed he
was A and was Alison's killer. It is later revealed that Ian liked to secretly
videotape the girls. When Spencer confronts Ian about Alison's death, he claims
he only pushed her, not intended for her to hit her head. After this he
approaches Spencer and tries to kill her, stating that he's doing it for
Melissa's benefit, but is killed by A, who surprisingly intervenes. His body
goes missing and he is presumed to be in hiding, however, his body is
eventually discovered, his death staged to look like a suicide; and leaving
Melissa with his unborn child. His killer is still unknown.