The cousin of missing Idaho siblings Joshua "JJ" Vallow and Tylee Ryan knows where they are but refuses to help law enforcement find them, her ex-husband alleges in a court document.
Lori Vallow Daybell's niece, Melani Boudreaux, is involved in a custody battle with her ex-husband, Brandon Boudreaux, over their four children in Maricopa County, Ariz.
In a court document filed in connection to that custody battle, Brandon claimed Melani "is involved in a cult where numerous members, adults and children alike, have been being killed off like flies."
Brandon also claimed in the document that Melani's "knowledge of the whereabouts of her aunt's two missing children and her unwillingness to cooperate with law enforcement in finding those children is daunting to [Brandon]."
In the document, Brandon also alleged that Melani conspired to kill him with her uncle, Alex Cox, in a drive-by shooting outside of Brandon's home in Arizona on Oct. 2. Cox, who is Lori Vallow's brother, died on Dec. 12 and his death is currently under investigation.
Melani and Brandon are due in court in Arizona on Thursday, according to court records. Steven Zachary, Melani's attorney, declined InsideEdition.com's request for comment on the allegations made in Brandon's petition.
An attorney for Brandon Boudreaux did not immediately respond to InsideEdition.com's request for comment Tuesday.
The document is Brandon's response to Melani's petition to modify legal decision making, parenting time and child support and was filed in February and published online by EastIdahoNews.com.
In the court document, Brandon Boudreaux claims that "it was only after the death of [Melani's] uncle that [Melani] chose to come forward in this case as she feels that her uncles' [sic] death will free her from any guilt she may have with respect to the attempted murder of [Brandon]."
Brandon and Melani's four young children have been living with Brandon following the Oct. 2 drive-by shooting attempt, which is currently under investigation by police in Arizona.
Rich Robertson, an Arizona-based private investigator with R3 Investigations, told InsideEdition.com Brandon Boudreaux hired him shortly after the Oct. 2 shooting to help find Melani and Cox.
"[Brandon Boudreaux] was so anxious that we actually met in my office on a Sunday morning and he told me this wild tale of killing and missing people and religious cults and that he had been the victim of a drive-by shooting," Robertson told InsideEdition.com earlier this month.
Robertson said he tracked Melani and Cox to Rexburg in early November after observing them packing Melani's things into a U-Haul while discarding some children's items on the curb in Arizona.
When Melani and Cox arrived in Rexburg, Robertson said one of his agents observed that while they saw Lori Vallow Daybell there, they did not see her children, JJ and Tylee.
"It was during that period that we realized we were seeing all the adults—Lori Vallow, Alex Cox, Melani Boudreaux—but we weren't seeing the kids. We weren't seeing JJ or Tylee," Robertson said.
JJ, 7, and Tylee, 17, have now been missing for more than five months. On Thursday, the children's mother was arrested by the Kaua'i Police Department in Hawaii.
Lori Vallow, also known as Lori Daybell, is currently being held there pending her extradition to Idaho. Lori has been charged with two counts of felony desertion of a child, as well as misdemeanor charges of resisting and obstructing an officer, solicitation of a crime, and contempt, according to the Madison County, Idaho, prosecutor's office.
Lori had been living in Hawaii with her fifth husband, Chad Daybell, an end-times author and publisher whose previous wife, Tammy, was found dead at their home in Rexburg on Oct. 19. Tammy's death is currently under investigation.
Chad has not been arrested or charged with a crime and both he and Lori have denied any wrongdoing.
An extradition hearing for Lori has been set for March 2.