Melissa Leo and Rosie O’Donnell have joined the cast of the HBO limited series “I Know This Much Is True,” along with Archie Panjabi, Imogen Poots, Juliette Lewis, and Kathryn Hahn.

HBO has given a production commitment to the six-episode drama, which stars and is executive produced by Mark Ruffalo. The family drama follows the parallel lives of identical twin brothers in a story of betrayal, sacrifice, and forgiveness, taking place against the backdrop of 20th century America. It is based on the book of the same name by Wally Lamb, who is also serving as an executive producer on the project.

Ruffalo stars as twin brothers Dominick and Thomas Birdsey, with Leo playing Ma (Concettina Ipolita Tempesta Birdsey), Dominick and Thomas’ mother. O’Donnell stars as Lisa Sheffer, a social worker at the Hatch Forensic Institute, where Thomas is staying. Additionally, Panjabi portrays Dr. Patel, Thomas’ newly appointed psychologist; Poots is Joy Hanks, Dominick’s live-in girlfriend; Lewis is Nedra Frank, a self-absorbed grad student hired by Dominick; and Hahn is Dessa Constantine, Dominick’s ex-wife.

Leo won an Oscar and Golden Globe for her performance in “The Fighter,” and received an Academy Award nomination for 2008’s “Frozen River.” She most recently starred in the Showtime dramedy “I’m Dying Up Here.” Leo is repped by Untitled Entertainment and CAA.

O’Donnell is known for appearing on talk series, including “The Rosie O’Donnell Show,” ABC’s “The View,” and “Rosie Radio.” She has also had a prolific career in film and television, with roles in movies like “A League of Their Own” and “Sleepless in Seattle,” and series such as “Will & Grace” and “The Fosters.” Most recently, O’Donnell starred in Showtime’s series “SMILF.” She is repped by WME.

Panjabi’s standout performance on CBS’ “The Good Wife” earned her an Emmy Award and three total nominations. She recently starred in and executive produced the six-part-drama “Next of Kin” in 2018. She is repped by Gersh.

Poots broke through in the film “28 Weeks Later,” and has also appeared in films such as “Jane Eyre,” “A Late Quartet,” and “Filth.” She is repped by CAA, Troika, and Narrative PR.

Lewis earned an Oscar and Golden Globe nomination for her role in Martin Scorsese’s “Cape Fear.” She has starred in critically acclaimed films like “What’s Eating Gilbert Grape,” “From Dusk Till Dawn,” and “August: Osage County.” Lewis is repped by Untitled Entertainment and UTA.

Hahn is a veteran of comedy films and television series, and recently received an Emmy nomination for her performance in Amazon’s “Transparent.” She also lent her voice to Columbia Pictures’ animated feature “Spider-Man: Into the Spider-Verse.” Hahn is repped by Gersh, Lighthouse Management, and Media and Schreck Rose.

“I Know This Much Is True” is written, directed, and executive produced by Derek Cianfrance (“Blue Valentine”). Also executive producing are Ben Browning and Glen Basner for FilmNation Entertainment, Gregg Fienberg, Anya Epstein, and Lynette Howell Taylor. It is co-executive produced by Jamie Patricof.