Alexis Denisof

Laura Leighton and Alexis Denisof have joined the cast of ABC Family’s hourlong pilot "Pretty Little Liars."

Ashley Benson, newcomer Shay Mitchell, Jean Louisa Kelly and Nia Peeples also have been cast in "Liars," joining Lucy Hale and Troian Bellisario.

In other ABC pilot castings, Tracey Fairway and Nick Robinson have joined Melissa Joan Hart and Joey Lawrence in their untitled multicamera comedy, and Vanessa Marano and Chloe Bridges have landed starring roles opposite Scott Cohen and Stephanie Childers the untitled Michael Jacobs single-camera comedy.

"Liars," based on Alloy Entertainment’s series of novels, revolves around four teen girls — Aria (Hale), Emily (Mitchell), Spencer (Bellisario) and Hanna (Benson) — who begin to receive mysterious messages, seemingly from a girlfriend who disappeared three years before.

Leighton ("Melrose Place") will play Hanna’s mother. Denisof ("Angel") will play Aria’s father, with Kelly ("Yes, Dear") and Peeples also playing parents.

Additionally, Bianca Lawson and APA-repped Torrey DeVitto and Sasha Pieterse have landed recurring roles in the pilot.

The untitled Hart-Lawrence project stars Hart as a political dynasty wild child-turned-politician who takes in her teenage niece (Fairway) and pre-adolescent nephew (Robinson) when her sister goes to prison and her brother-in-law flees. She turns for help to Jack (Lawrence), who, desperate for a job, moves in and becomes the family’s "manny."

In the Jacobs project, a young dad (Cohen) recently laid off from his architecture firm begins to identify with and mentor his underdog middle daughter (Marano) as his veterinarian wife (Childers) shares a closer bond with their Type-A older daughter (Bridges).

Valerie Tian ("Juno") has been tapped to play the best friend of one of the girls.