JULIA ROBERTS gushes over her bliss at being a wife and mom, but The ENQUIRER has uncov­ered the dark secret of her own childhood – her stepfather was an abusive drunk and accused child molester!

Sources say the Hollywood beauty “feared and despised” her stepfather Michael Motes, an alcoholic with a violent temper who turned her for­mative years into a nightmare.

The “Pretty Woman” star, 46, refus­es to discuss Motes, who was married to her mother Betty from 1972 to 1983.

But he’s been accused of sexu­ally molesting a 13-year-old boy while raising Julia and blackmailing the teen into having gay sex for five years.

The ENQUIRER has learned Motes, a retired antique dealer, lives an openly gay life with another man and plans to write a blockbuster tell-all that’s sure to throw disturbing new light on Julia’s troubled child­hood.

Her mother Betty divorced Julia’s biological father Walter in 1971 and soon wed Motes, now 67. But his alco­holism quickly ruined their marriage.

“Motes was a nasty piece of work,” a source close to the family told The ENQUIRER.

“When he was drunk, he often had raging arguments with Betty and the children. He once threw Julia’s Walkman against the wall and smashed it. Julia often stayed at friends’ houses to escape him.

“He didn’t have a job and Betty worked all the time to keep the family afloat.”

While Julia has nothing to say about her stepfather, her older brother, actor Eric Roberts, has blasted Motes openly.

“It was common knowledge where we grew up that Motes was a freak,” Roberts said in an interview.

“(He) terrorized and abused me, and I fear he terrorized my sisters, Julia and Lisa, as well.”

Author James Spada wrote in the 2004 biography, “Ju­lia: Her Life,” that the Oscar-winning actress “feared and despised” Motes and that he “at least, alternately ig­nored, pushed around, and denigrated his two stepdaughters.”

Even worse, Motes was accused of molesting a 13-year-old boy in the family home when Julia was 10.

In a 1992 interview, Shawn Melton claimed Motes blackmailed him into hav­ing gay sex for five years, used him as a sex slave and even passed him around to a gay pal, who also molested the youngster.

Melton confirmed the story to The ENQUIRER, and described Motes as “a serial abuser of children” in an email.

“I was trying to get him charged with a crime,” Melton wrote in the email. “But I was never successful.”

Alarmingly, Motes appears to main­tain contact with children, posting a picture of himself with two unidenti­fied tots on his Facebook page.

After divorcing Julia’s mother, Motes came out as gay and now shares a condominium with his partner Timothy Raasch in Marietta, Ga., just six miles from the home where he raised Julia.

When contacted by The ENQUIRER, Motes said: “I do not give interviews.”

Asked specifically about the sexual abuse allegations, he said: “There are a lot of mis­conceptions. I’m writing a book about my life that will tell my side of the story.”

The ENQUIRER has also learned that Motes is obsessed with the clas­sic novel “Gone with the Wind” and claims to be distantly related to the book’s author Margaret Mitchell, sources say.

“He has a large collection of ‘Gone with the Wind’ memorabilia, and once leased part of the Marietta Museum of History to display it,” said Connie Sutherland, director of the Gone with the Wind Museum in Marietta.

When Julia was a child, Motes of­ten dressed in a Confederate uniform and dragged his stepdaughters to Civil War-related events.

But like a true actress, Julia hid her troubled home life from friends, pals say.

“I remember Julia’s stepdad,” Paula Monteith, 46, a classmate of Julia’s at Campbell High School in Smyrna, told The ENQUIRER.

“He was very tall and at one point he shaved his head. I remember thinking he looked like Mr. Clean.”

If Julia had problems at home, “she didn’t talk about it,” said Monteith. “I guess that she dealt with it inter­nally.”

Ironically, Julia’s dysfunctional upbringing mirrors the story line of her upcoming film “August: Osage County,” a searing drama about combative family relationships that co-stars Meryl Streep.

But while promoting the film, Julia – who has three young children with husband Danny Moder – gushed over her own brood.

“It’s my privilege and honor to cook three meals a day for my family,” she said. “You have pride in how you take care of your family.”