A relative of the two Idaho children missing for five months — whose doomsday-obsessed mother was recently arrested — allegedly knows where they are, but won’t cooperate with authorities, new court documents claim.

Melani Pawlowski “is under investigation” relating to the disappearance of her aunt Lori Vallow’s kids, 17-year-old Tylee Ryan and 7-year-old Joshua “JJ” Vallow, who vanished in September, according to the document filed by her ex-husband in Arizona last week.

“Melani’s knowledge of the whereabouts of her aunt’s two missing children and her unwillingness to cooperate with law enforcement is daunting,” the papers state.

The document, obtained by local outlet Fox10, stems from a contentious child custody battle between Pawlowski and her ex, Brandon Boudreaux.

Boudreaux accuses his ex-wife of being involved in the same cult as Vallow, “where numerous members, adults, and children alike, have been being killed off like flies” and claims she plotted a failed hit on him in October.

“Brandon believed Melani … had a million dollars of reasons to have him killed … hoping to cash in on the policy to help support the cult that she is believed to be a part of,” the document alleges.

In another passage of the filing, Boudreaux claims Pawlowski told her current husband, Ian Pawlowski, that “sometimes children are full of light and then just like that they go dark.”

The document was filed in Maricopa County on Wednesday, a day before Vallow, 46, was arrested in Hawaii and hit with a slew of charges, including felony desertion and nonsupport of dependent children.

She was being held on $5 million bond with an extradition hearing set for March 2.