Ben's estranged wife Jennifer Garner, the mother of his three children, staged an intervention last month, and drove the actor to rehab so he could complete a treatment program for the third time.
During an interview with Entertainment Tonight, Oscar winner Casey candidly discussed his big brother's battle with booze.
"Alcoholism has a huge impact on not just the person, but also their family. So, I think for his kids' sake and for their mom, and for himself, he's trying to do the work and get it together," the 43-year-old explained.
Revealing that he and Ben come from a "long line of alcoholics," Casey confessed it was going to be a hard fight ahead for his brother.
"Ben is an addict and an alcoholic. Most of my grandparents are alcoholics. My father is an alcoholic, as bad as you can be, and he's been sober for about 30 years. I've been sober for about six years," he said.
"Ben is trying to put it together, and it can be a very hard thing to do. He has the kind of resources and time, luckily, to take the time and go to a good facility."
The "Argo" star has been spotted during his visits home from rehab, and Casey praised his 46-year-old big brother for being honest about his alcoholism.
"It can't be easier to have everybody looking at you and taking your picture as you're walking out of an intervention. I don't envy that," he admitted.
"I saw my father struggle with it for many years and nobody was following him around with cameras and stuff. It's not a great look. But on the other hand, it's nothing to be ashamed of and it's good that he's taken care of."