The grandparents of missing Idaho 7-year-old Joshua "JJ" Vallow are pleading for the safe return of the boy and his sister, Tylee Ryan, 17.
Larry and Kay Woodcock traveled from their home in Louisiana to Idaho to help FBI agents with their investigation and announce a $20,000 reward for information leading to the missing siblings, who were last seen on Sept. 23 in Rexburg, Idaho.
"JJ is my heart and I am hoping this will allow one person—one person—to simply say, 'I saw them, I know where he's at,' and give us that information so we can bring JJ and Tylee back," Larry Woodcock told reporters during a press conference Tuesday.
The couple have also launched a website, FindJJandTylee.com, to help collect leads.
Joshua last attended Kennedy Elementary School in Rexburg on Sept. 23, authorities said. He has brown hair and brown eyes, is 4 feet tall and weighs 50 pounds. He has autism and "may be in need of medical attention," according to authorities.
Tylee Ryan has blonde hair and blue eyes, is 5 feet tall and weighs 160 pounds. Neither Joshua nor Tylee had been reported missing to any law enforcement agency before police launched their search following a Nov. 26 welfare check on the home where they lived with their mother, Lori Daybell.
Kay and Larry Woodcock said they used to speak with JJ all the time, but the last time they FaceTimed with JJ in August, it seemed like someone else was holding the device and the call lasted less than a minute. The couple never heard from JJ again.
“We don’t know why we weren’t allowed more access to him, but we reached out constantly in every way – email, voicemail, text, phone call, whatever – and never, ever got a response, so that was very concerning to us," Kay Woodcock said during the press conference.
The children's mother, Lori Daybell, and her fifth husband, Chad Daybell, have been named persons of interest in their disappearance, but no arrests have been made. Authorities are also looking for the couple, who left Idaho when police came to search their home. They had initially said JJ was staying with family friends in Arizona, but police discovered that was not true.
Since then, police say Lori Daybell, has "completely refused to assist this investigation," something that baffles and angers her family.
"I can't comprehend that Lori is refusing to say where the kids are, I just don't understand it," Kay Woodcock said. "I just plead with her to please just let us know where the kids are. It's not difficult, and it will end all of this."
Police believe Lori knows where the children are or what happened to them.
"We know that the children are not with Lori and Chad Daybell and we also have information indicating that Lori knows either the location of the children or what happened to them," Rexburg Police Chief Shane Turman said in a statement Monday. "Despite having this knowledge, she has refused to work with law enforcement to help us locate her own children. Lori Vallow has chosen instead to leave the state with her new husband."
An attorney for the couple, Sean Bartholick, issued a statement on behalf of the couple on Dec. 23.
“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," Bartholick wrote in the statement.
Bartholick did not respond to InsideEdition.com's request for comment.
Chad is a member of the Church of Jesus Christ of Latter-day Saints. He has published books about his faith and near-death experiences, as well as fictional stories set in an apocalyptic United States.
Both Chad and Lori Daybell's previous spouses died recently. On Oct. 19, Chad's ex-wife, Tammy Daybell, 49, was found dead in her home, police said. At the time, her death was believed to be from natural causes. Chad Daybell married Lori just a few weeks later.
Lori Daybell's ex-husband, Charles Vallow, was shot and killed by Lori's brother, Alex Cox, on July 11, The Arizona Republic reported. Cox died on Dec. 12, and his cause of death has not been made public, according to the paper. An investigation into his death is ongoing.
Investigators say they believe the siblings are in danger. In his statement Monday, Rexburg Police Chief Turman said, "We are aware in the weeks after Tammy Daybell's death, Lori Vallow/Daybell and Chad Daybell told witnesses that Lori's daughter had died a year before the death of her father, which is untrue. Around that same time, Chad told another witness that Lori had no minor children."
Larry and Kay Woodcock believe the siblings are still alive and are working around the clock to bring them home.
"We don't say the 'd word,' we don't want to, we're not going to, because we truly believe and we hope and pray these kids are alive," Larry Woodcock said. "All I want before I go is just to see those children.
"I just want to hear him beat on the drums, I want to hear him say, ‘Papa, let’s go ride’ or ‘Let’s go to Checkers and let’s go get a hamburger.’ I’m hoping beyond hope that that happens in the near future," he continued.
The Rexburg Police Department asks anyone with information regarding the children's whereabouts or welfare to contact the department at 1-208-359-3000 or the National Center for Missing and Exploited Children (NCMEC) at 1-800-THE-LOST.