"We still believe in Joran," said his father, Paul van der Sloot.
In an exclusive interview with FOX News' Greta Van Susteren, the van der Sloots said that their prayers were with the family of 18-year-old Alabama woman who vanished in Aruba (search). Anita van der Sloot, the Dutch suspect's mother, was wearing a bracelet that said "Hope for Natalee," which she received from Natalee's mother.
But the pair stressed that they also were going through an ordeal.
"It's a nightmare for us, too," said Anita van der Sloot, whose son, 17, is in jail in connection with the disappearance.
Sometimes too emotional to speak, Anita described how prison guards were putting "a lot of pressure" on Joran during interrogations, some of which lasted "10 hours."
The questioners did "things like calling him 'psychopath, murderer, tell us where you buried the girl. You're a criminal. I can't beat you, but if I could beat you I would do this.' … Extreme things," said Anita.
She described her son as "a very outgoing person" who received all "A"s and "B"s in advanced courses at school.
"He's a sweetheart. To me, he's very warm," she said.
Recounting a visit to her son in jail — she is allowed to visit Joran, but her husband is not — she said she couldn't stop herself from crying, and Joran tried to reassure her of his innocence.
"'Mom, don't worry ... the truth will come forward and I know that I didn't do anything to the girl,'" said Joran, according to his mother. "He was so strong. And I believe in him. I believe so in him."
When asked if Joran had ever been involved in drugs, Anita said: "A hundred percent, no."
Despite the suspect's parents' emotional interview, Natalee's stepfather, also appearing on "On the Record," said the missing teen's mother, Beth Holloway Twitty (search), was having a much harder time.
"I understand her feelings, but Beth's feelings are ten times worse," George Twitty told FOX News.
George Twitty said that in the initial days after the teen's disappearance, Paul van der Sloot — and one of two Surinamese brothers arrested with Joran van der Sloot — advised his son not to talk to her family.
"He and the other boy kept saying 'you say nothing,'" Twitty said. "I know that the father and I know that the son knows a lot more than they're saying."
Joran van der Sloot and two friends were arrested 10 days after Holloway disappeared on May 30. Police say Joran van der Sloot met Holloway at a casino two days earlier. They say the three young men testified that they took her from a popular restaurant to a beach, where the Dutch boy and Holloway were kissing in the back of the car, then dropped her at the Holiday Inn where she was staying around 2 a.m.
Beth Holloway Twitty has insisted that the three know what happened to her daughter and that police should press them harder to tell the truth. She has asked why the three were initially released after only a couple of hours of questioning, and arrested more than a week later.
Anita van der Sloot also questioned that tactic. She told FOX News: "Joran should have been interrogated from the beginning. But they let the kids go."
Holloway's father, meanwhile, said Wednesday he was confident that the investigation into her disappearance was close to being resolved. But dozens of searches by officials and volunteers have failed to turn up any trace.
His daughter disappeared on the last day of a five-day trip to celebrate her high school graduation with other students. Her passport and packed bags were found in her room.
"I'm optimistic," Dave Holloway said during an interview with Associated Press Television News. "The FBI indicated to me that the (Aruban) police are very adequate and doing a good job. "
Aruba government spokesman Ruben Trapenberg defended the island's response to the vanishing on FOX Thursday. "Our law enforcement officials get most of their training in the U.S. and in Holland," Trapenberg said, in response to recent complaints that the island has insufficient resources.
Trapenberg also said Aruba welcomes the Texas EquuSearch Mounted Search and Recovery Team, which the Holloway family has called in to help with the search for the woman.
Dave Holloway said he also believed the three young men held the key to his daughter's disappearance.
"These three guys cannot commit a perfect crime," he said.
A fourth man detained in the case, 26-year-old party boat disc jockey Steve Gregory Croes (search), said he knew one of the two Surinamese brothers arrested with Joran van der Sloot from an Internet cafe, according to his boss, Marcus Wiggins. Wiggins' boat, the Tattoo, docks near the Holiday Inn.
FOX News' Greta Van Susteren, Jared Goldman and The Associated Press contributed to this report.