Lori Vallow's niece may be withholding information on the whereabouts of the 'cult' mom's missing children from investigators, new court documents suggest.

Melani Pawlowski was tied to the disappearance of Lori's children Joshua 'JJ' Vallow and Tylee Ryan in late December when her ex-husband, Brandon Boudreaux, claimed that she'd followed her aunt into a dangerous doomsday cult and suggested their radical religious beliefs played a role in the case.

Brandon and Melani have been embroiled in a bitter custody battle over their four young kids since the mother suddenly filed for divorce over the summer.

In a new court filing, Brandon states: 'Melani is involved in a cult where numerous members, adults and children alike have been being killed off like flies.'

He further alleges that his ex-wife knows where JJ and Tylee are but is refusing to cooperate with the investigation.

'Melani's knowledge of the whereabouts of her aunt's two missing children and her unwillingness to cooperate with law enforcement is daunting,' the filing obtained by FOX10 states.

It also claims that Melani's current husband Ian Pawlowski, whom she married on November 30, had told law enforcement that she 'says sometimes children are full of light and then just like that they go dark'.

Lori Vallow's niece Melani Pawlowski may be withholding information on the whereabouts of the 'cult' mom's missing children from investigators, according to new court documents filed by Melani's ex-husband Brandon Boudreaux (above together)

Joshua 'JJ' Vallow, seven, and Tylee Ryan, 17, were last seen in Idaho in September in Rexburg, Idaho, and authorities are still searching for them

Lori arrested Thursday in Kauai on charges of child abandonment and desertion after she failed to comply with a court order to produce JJ and Tylee to authorities in Rexburg, Idaho, by January 30. She is pictured in court on Friday night

Brandon's filing came to light days after Lori was arrested Thursday in Kauai on charges of child abandonment and desertion after she failed to comply with a court order to produce JJ and Tylee to authorities in Rexburg, Idaho, by January 30.

She is being held in lieu of $5million bail while awaiting extradition to Idaho.

Lori and her doomsday author husband Chad Daybell, whom she married weeks after her children went missing, fled Rexburg in late November, hours after police began asking questions about where her children were.

Police say the couple have refused to cooperate with investigators and have repeatedly lied about where the children are.

They became the target of a national media firestorm with the revelations that police are also investigating the mysterious deaths of both of their previous spouses and Lori's brother, as well as family members' claims that they are members of a dangerous doomsday cult.

Brandon has long held that Lori's alleged cult ties were linked to the disappearance of her children and the three deaths, as well as an attempt on his own life last fall.

He was targeted in a drive-by shooting on October 2, just as he arrived home from the gym in Gilbert, Arizona.

Brandon told investigators he saw a rifle with a silencer emerge from the backseat of a 2018 Wrangler Jeep seconds before a bullet shattered the driver's side window of his Tesla, missing his head by inches.

Police later determined that the Jeep was registered to Charles Vallow, Lori's former husband who was shot dead by her brother Alex Cox in July.

The new court filing states: 'Brandon believed Melani, his wife at the time, 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.

'Melani left Arizona almost immediately after the attempt on his life, leaving without a trace and leaving her children behind.'

The filing was in response to a recent petition Melani filed to amend their custody agreement.

Brandon alleges that Melani is seeking the amendment now because 'she feels that the suspicious death of her uncle, Alex, ... has somehow freed her from her role in the attempt on Brandon's life.'

Alex Cox died on December 12 at a home in Gilbert. His death is under investigation and the results of an autopsy to determine the cause have not yet been released.

Brandon and Melani have been embroiled in a bitter custody battle over their four young kids since the mother suddenly filed for divorce over the summer. In a new court filing, Brandon states: 'Melani is involved in a cult where numerous members, adults and children alike have been being killed off like flies'

Brandon said his marriage to Melani deteriorated after she joined her aunt Lori's 'cult' around June 2018. Boudreaux and Melani are pictured at their wedding in 2008

Brandon revealed in a December interview (pictured) that he believes Lori's alleged cult ties were linked to the disappearance of her children and the three deaths, as well as an attempt on his own life last fall

Lori's estranged husband Charles Vallow (pictured together) was shot dead by her brother Alex Cox in Arizona on July 11

Chad's wife Tammy Daybell (pictured together) was found dead under mysterious circumstances in October, just two weeks before he married Lori

A search warrant uncovered earlier this month suggested that Cox may have been under investigation for homicide in connection with the fatal shooting of Lori's estranged husband Charles on July 11.

Charles, who filed for divorce months earlier, had gone to Lori's home in Chandler, Arizona, to pick up JJ, the couple's adopted son, when they got into an argument that turned physical.

Lori's brother Alex Cox died under mysterious circumstances on December 12

Cox told police that he intervened and Charles hit him with a baseball bat. He then went to get his gun and shot Charles two times in the chest.

Police initially determined that Cox acted in self-defense, but the investigation was reopened amid a multi-state search for JJ and Tylee.

Weeks after Charles' death, Lori moved her children from Arizona to Idaho, where her soon-to-be husband Chad lived with his then-wife Tammy.

Tammy was found dead under mysterious circumstances on October 19.

The 49-year-old's death was initially ruled as natural causes but an investigation was opened after police learned about Chad's quick marriage to Lori while searching for her kids.

Tammy's body was exhumed on December 11 and the results of her autopsy have not yet been released.

Lori is seen in two new mugshots taken after her arrest in Hawaii on Thursday

Police are seen frisking Lori before she was taken into custody outside her Kauai apartment

As officers prepared to take Lori away in a patrol car, her Doomsday author husband Chad Daybell (right) watched helplessly

Lori was arrested in Kauai on Thursday evening and appeared in court the following day, where a judge ruled against her motion to reduce her $5million bail.

Her attorney Dan Hempey had argued that Lori's bail bond be lowered to at least $10,000, saying that she was not a flight risk and did not have a passport.

Hempey also scolded authorities for taking Lori into custody so publicly, after photos of the arrest outside her rented apartment were published by media outlets nationwide.

'We remained willing to produce her as soon as police wanted her to be produced,' her attorney Dan Hempey said.

'Instead, she was arrested and media was calling us all day. It seems like it was a made for media event at the taxpayer's expense.'

In response, the prosecution cited charges that imply she poses a risk to the community and will engage in illegal activity.

'She has no ties to this island, apart from a rented condo,' the prosecution argued. 'If ever there was a case suitable for a person to be denied bail, this is the case'.

The judge denied the request - pointing out that Lori had already fled from Idaho, where the charges were filed, and that she is accused of obstructing justice.

Lori is scheduled to appear again in court on March 2 for an identity hearing - the next step in the extradition process which could take up to 90 days.

Her husband Chad sat in the public gallery during the hearing.

He had refused to answer reporters' questions outside the court.

Lori appeared in court Friday, where a judge ruled against her attorney's motion to reduce her $5million bail to $10,000

Chad is seen in the courtroom during his wife's hearing on Friday

The court appearance came as new details emerged of the last-known whereabouts of Lori's missing children, revealed in an affidavit filed two days before the arrest by Rexburg Police Detective Ron Ball.

Tylee, it has been revealed in court documents, was last seen on September 8 when police believe that Lori took her on a day trip to Yellowstone National Park, which straddles the border between Idaho and Wyoming.

Police say that they have a photograph, taken from Lori's iCloud account, of Tylee at the park entrance.

JJ was last seen at school in Rexburg on September 23.

The documents reveal the last known footage of the seven-year-old, recorded on a neighbor's security camera, showed him playing outside his home on September 17.