An 11-year-old California girl kidnapped in 1991 while waiting for a school bus has been found alive, and a convicted sex offender is accused of raping and fathering two children with her while he and his wife held her captive in their backyard.

Despite the shocking revelations, the discovery of Jaycee Lee Dugard brought sudden relief to her family 18 years after their young girl disappeared.

Dugard had been kept with the two girls, ages 11 and 15, in a series of tents and sheds hidden behind the Antioch, Calif., home of Phillip and Nancy Garrido, the El Dorado County Sheriff’s Office said Thursday at a news conference. The couple has been arrested on several charges stemming from the discovery.

Dugard and her two daughters are "in good health, but living in a backyard for the past 18 years does take its toll," Undersheriff Fred Kollar said.

Now 29, Dugard was reunited Thursday with her mother, who was overjoyed to learn the ordeal was over and the daughter she feared dead was actually alive and well.

Dugard's stepfather, Carl Probyn — the last person to see her in 1991 and a longtime suspect in the case — said he was overwhelmed after doing everything he could to help find her. He said the news that she was found was like winning the lottery.

"To have this happen where we get her back alive, and where she remembers things from the past, and to have people in custody is a triple win," Probyn, 60, told The Sacramento Bee.

The Garridos were arrested Wednesday after Phillip Garrido raised suspisions of campus police at the University of California, Berkeley. Garrido was spotted there with two young girls trying to gain access to the campus library, Kollar said.

Campus police then notified Garrido's parole officer who arranged an interview. Garrido, who was on parole from a 1971 conviction for rape and kidnapping, arrived for the meeting accompanied by the two girls, as well as wife and another woman, named Allissa.

Allissa later was identified as Jaycee Dugard, the blond, pony-tailed 11-year-old who was taken from the school bus stop minutes after she left her South Lake Tahoe home in 1991.

"None of the children have ever been to school, they've never been to a doctor," Kollar said. "They were kept in complete isolation in this compound."

The Garridos are being held in the Contra Costa County Jail in Martinez on potential charges of kidnapping and conspiracy on Wednesday, police said. Phillip Garrido also could face charges of rape by force, lewd and lascivious acts with a minor and sexual penetration.

Click here for more on this story from FOX40.com.

At the Garrido's house, barriers were constructed to "inhibit outside viewing and prevent the victims from contact with the outside world," Kollar said.

Garrido was on lifetime parole and his arrest raises questions about how closely parolees are monitored. But Kollar said a parole officer who had visited Garrido's house previously had not noticed anything amiss — the compound was well concealed by shrubs, garbage cans and a tarp.

The neighborhood is described as a residential area, with the Garridos home raising no suspicion from the outside world as to the horrific compound concealed in the backyard.

Neighbor Helen Boyer, 78, described the Garridos as nice and friendly and said they cared for Phillip Garrido's elderly mother.

"If I needed something, they would be the first I would call on," Boyer said.

Dugard left for school the morning of June 10, 1991, dressed all in pink and stood at the bus stop two blocks from her house. As her stepfather watched from the driveway, a gray car with two people inside pulled up, grabbed the child and sped away, according to witnesses.

In media reports at the time, the girl's stepfather said he heard Jaycee scream then jumped on a bicycle and frantically pedaled after the car in a failed effort to follow it up a hill. He then turned around and shouted at neighbors to call the police.

The case attracted national attention and was featured on TV's "America's Most Wanted," which broadcast a composite drawing of a suspect seen in the car.

Click here for more on this story from KTVU.com.

The Associated Press contributed to this report.