As the cute little brother on the '80s sitcom "Growing Pains," Jeremy Miller practically grew up on television . But a decade after the show ended, the former child star revealed he had kept a long-running secret about his personal life: He struggled with alcoholism for many years, a struggle that he admits began even before he stepped into his first memorable TV role.

"I began drinking at 4 years old," Miller tells "Oprah: Where Are They Now?" in the above clip. "My grandparents used to throw a lot of parties, and I would run around after the parties and finish off all the empty beers."

Before he had even reached his teen years, Miller says he had begun getting drunk.

"I didn't really mess around with it after that until I was around 12," he says. "That was the first time I ever got hammered."