Casey Affleck is staying positive about his brother's path to sobriety.
The Oscar winner stopped to talk with ET's Keltie Knight at the premiere of his new comedy The Old Man and the Gun at the Toronto International Film Festival on Monday, and he addressed his brother Ben Affleck's health and recovery.
"He’s doing great," Casey, 43, shared. "He’s in rehab and he’s recovering and seems to be doing well."
The Justice League star entered rehab on Aug. 22, following the 46-year-old actor's recent outings with 22-year-old Playboy model Shauna Sexton, whom he has been casually seeing in the wake of his split with Saturday Night Live producer Lindsay Shookus.
Ben was admitted for addiction recovery treatment at a facility in Malibu, California, and has been receiving visits from Sexton during his stay.
A source recently told ET that the actor's high-profile relationship with the Playboy playmate has been a point of contention among his close friends.
"He had stayed in touch with Shauna the entire time he was in rehab, and the people at the facility and friends had huge concerns about it because she isn't sober," the source said. "She is a huge red flag to everyone that is trying to support Ben with his process. Shauna is giving him false confidence and that is their biggest concern."
Affleck's ex-wife, Jennifer Garner, is also "frustrated" with the situation, the source told ET. "Jen knows he is back at the house with Shauna and she is so painfully frustrated. She knows he has to do this for himself."
For more on the actor's struggle with sobriety and new relationship, watch the video below.
Casey's upcoming comedy The Old Man and the Gun -- starring Robert Redford, Sissy Spacek, Danny Glover, Elisabeth Moss, John David Washington and Tika Sumpter -- hits theaters Sept. 28.