By Mandi Bierly
March 09, 2009 at 01:55 PM EDT

Nate Corddry (Studio 60 on the Sunset Strip) and Molly Parker (Deadwood, Swingtown) have been cast as Sarah Michelle Gellar’s siblings in the HBO pilot The Wonderful Maladys. According to The Hollywood Reporter, Corddry will play her younger “bookish grad student” brother, while Parker will take the role of her older therapist sister. The siblings lost their parents at an early age. The show follows their dysfunctional lives as adults in New York. When the project was announced last September, screenwriter Charles Randolph, who penned the dramedy for Gellar, described her character as having “a kind of zealous immaturity — like a drug addict with a to-do list.”