REXBURG, Idaho (WCMH/CNN) — A nationwide search for two missing children from Idaho continues into Christmas Eve.

7-year-old Joshua ‘JJ’ Vallow and 17-year-old Tylee Ryan have not been seen or heard from since September, KTVX reported.

Their mother, Lori (Vallow) Daybell, and stepfather, Chad Daybell, are now on the run. Police in Rexburg, Idaho named the couple ‘persons of interest’ in the disappearance of the children.

“We haven’t been able to make contact with him in the last couple of weeks,” said Assistant Chief Gary Hagen with the Rexburg City Police Department.

According to police, the Daybells had refused to help authorities find the children. The couple went missing during a police investigation in November.

At that time, police said the couple had lied to investigators and said one of the children was staying with a family friend in Arizona.

Family members notified police after both Joshua and Tylee had not been seen or heard from in months.

“The last time anyone had seen the kids were somewhere around the 23 or 24 of September,” said Hagen.

Chad Daybell is under investigation after his former wife, Tammy Daybell, was found dead in their home in October.

While she was initially thought to have died from natural causes, officials said Tammy Daybell’s remains have since been exhumed and an autopsy is being conducted as authorities investigate what may be suspicious circumstances surrounding her death.

Brandon Boudreaux, who married into Lori Vallow’s family, told KSTU he believes new religious beliefs led to the deaths of multiple family members along with the disappearance of the children.

“I spent the last 11 years of my life spending time with Lori and her now-deceased husband Charles,” Boudreaux said. “I don’t know what happened to those kids, but I know there’s people who do, and they’re not talking… I love them both. I hope they’re safe. They’re both just innocent and they didn’t deserve to be involved in any of this.”

Boudreaux told the station his wife, Lori Daybell’s niece, followed her aunt in joining what he described as a cult with Chad Daybell. Chad Daybell is a self-proclaimed Latter-day Saint author of religious books detailing the end of the world.

“You can’t be a member of the church and believe those things,” Boudreaux said. “I think it’s an infatuation with the end of the world and an infatuation with power, and they’re using it to try to make money off of people’s beliefs.”

An attorney for the Daybells told East Idaho News he has been in contact with the couple, but did not have any information on the whereabouts or welfare of the children.

“Chad Daybell was a loving husband and has the support of his children in this matter. Lori Daybell is a devoted mother and resents assertions to the contrary. We look forward to addressing the allegations once they have moved beyond speculation and rumor.”

Lori Daybell is described as 5’6″, with blonde hair and blue eyes.

Chad Daybell is 6’3″, with brown hair and blue eyes.

Joshua Vallow is 4 feet tall, with brown hair and brown eyes and responds to the nickname JJ.

Tylee Ryan is about 5 feet tall, with blonde hair and blue eyes.

Anyone with information is asked to call Rexburg police at 208-359-3000 or report it to the National Center for Missing and Exploited Children.