Sean Astin's Childhood With Patty Duke

July 31, 2004 -- In The Lord of the Rings he cheated death, fought enemies and helped bring a gold ring to its destruction. But before taking on the role as Frodo's trusted sidekick, Sean Astin survived a struggle of a far more personal sort.

The rising star endured a childhood on the edge of destruction.

He grew up as the child of two Hollywood stars: Oscar winner Patty Duke who gets a star on the Hollywood Walk of Fame this month, and actor John Astin, who played The Addams Family patriarch Gomez. But his home life included Duke's battle with manic depression — and the shocking news that Astin was not his real father.

Talking About Troubling Times

Sean and his younger brother Mackenzie are speaking publicly for the first time about growing up in the shadow of their mother's illness, with some details included in the upcoming memoir, Sean Astin, There and Back Again an Actors Tale.

The two brothers tell 20/20 what it was like growing up with a mother who was emotionally unstable. They were present during several of her suicide attempts.

It was Sean, the older and more resilient child, who was most often the target of their mother's manic rages. He recalls an incident when he cleaned his room while building a model airplane so his mother would not get mad; instead, she was infuriated that he was trying to be too perfect.

"I could hear the sound of Mom sort of going through the hallways like, you know, the beast in Beauty and the Beast," said Astin. "And she came in with this glass of water and … throws the water in my face. And then she destroyed the model."

The sons referred to these incidents as their mother's "freakouts."

But his mother wasn't like that all the time, Sean says. "This woman is a powerful, strong woman, who wanted us to grow up independent and confident and strong … 99 percent of the time."