Joshua "JJ" Vallow and Tylee Ryan have been missing for five months and their mother, Lori Vallow, has not cooperated with court orders to produce them.
The children were last seen in Idaho in September, but the case also has ties to Arizona and Hawaii, where Lori and her new husband Chad Daybell were recently found by police.
Lori and Chad have been named persons of interest in the case, but they have not been arrested.
The head-scratching case will be featured on "Dateline NBC" on Friday, which can be seen on 12 News.
"Dateline" will feature an interview with April Raymond, who had considered herself a close friend of Lori Vallow.
Raymond told host Keith Morrison that Lori is "telling people (that) there's a lot of media hype around her right now and she's waiting for that to die down.
"I don't know if I would describe it the same way," she added. "I would describe it as something a little more serious, a lot more serious."
Here is the latest news regarding the disappearance of Joshua "JJ" Vallow and Tylee Ryan: