TAMPA, Fla. (NBC/WFLA) — Gabby Petito’s parents and stepparents opened up to Dr. Phil about their desperate attempts to find answers about their daughter’s death.

The family told Dr. Phil that when they stopped hearing from Gabby, they first called and texted Brian Laundrie’s parents, but the couple never replied.

“A normal parent, when you text someone that ‘you’re gonna call the cops cause you can’t find your child’ they would reply,” Gabby’s father Joseph Petito said. “No response. No nothing.”

“I do believe they know a lot more information than they’re putting out there,” Petito’s mother Nichole Schmidt added.

When asked about the Petito’s family’s claims, a lawyer for the Laundrie family told NBC “no comment.”

Laundrie’s sister Cassie also sat down for an interview this week and opened up about the case.

“I don’t know if my parents are involved,” Cassie Laundrie told Good Morning America. “I think if they are, then they should come clean.”

An attorney for the Laundrie family has told NBC in the past that Brian’s parents did not assist in his disappearance and don’t know where he is.

According to the family’s lawyer, Brian left Utah on Aug. 17, five days after the couple had a dispute and was stopped by police. The lawyer said Brian then flew back to Utah on Aug. 23 to rejoin Petito on their cross-country road trip.

He drove back to his family’s North Port home alone with the van the couple had been traveling in.

Petito’s remains were found on Sept. 19 near a campground in Wyoming’s Bridger-Teton National Forest. Laundrie’s parents now say they last saw him on Sept. 13, one day earlier than previously thought. They told police he went for a hike in the Carlton Reserve and never returned.

Petito’s family told Dr. Phil they believe he is still out there and shared one simple message for Brian: “Turn yourself in.”

“You’re only making it worse. For us, and for himself, and for his family. Let us have some closure,” Petito’s stepfather Jim Schmidt said.

Petito’s family said Gabby and Brian used to camp and hike along the Appalachian Trail and spent time in the North Carolina woods. There have been around a dozen reported sightings of Laundrie in that area, according to reports.

“He was acting funny and I wasn’t sure about what he looked like and then I got—I went and parked and pulled up the photographs of him and I’m 99.99% sure that was him,” one 911 caller reported.

“The Haywood County Sheriff’s Office has received a number of calls regarding the sighting of Brian Laundrie over the past several days, each one being investigated thoroughly and areas of concern searched, but all to no avail,” the agency said on Facebook Monday. “We will continue to respond and fully investigate all calls for service related to the nationwide search for Mr. Laundrie within our jurisdiction.”