The death of a man previously married to Lori Vallow, the mother accused of conspiracy in connection with the deaths of her two children, is under review, fueling questions about the so-called "cult mom" has a connection to the case.

Phoenix police have confirmed to Fox News that they are reviewing an investigation into the April 2018 death of Joseph Ryan, Vallow's third husband. The couple divorced 14 years prior to his death.

The inquiry comes days after several news outlets published an audio recording released by Ryan's sister, Annie Cushing. In it, Cushing claimed, Vallow is heard talking about wanting to kill Ryan amid a custody battle over their daughter, 16-year-old Tylee Ryan,  according to the Daily Mail. Tylee was one of the children found dead earlier this year,

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“He was constantly trying to get custody of my 3-year-old daughter,” Vallow allegedly said in the recording. “If he comes against you once, if he comes against you twice, if he comes against you three times then you can kill him, it says it in the scriptures.” 

Cushing told Fox Nation host Nancy Grace that she had kept contact with Vallow after the divorce, but Vallow had not notified her of her brother's passing. 

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"Lori and I maintained contact over the years, but she never told me that Joe had died," Cushing said in a new episode of Fox Nation's "Crime Stories with Nancy Grace."

"I had found out through a relative being forwarded one of these letters where they were seeking family members. And so it's my understanding that by the time I found out, he had already been cremated, so I think it was because he was an unclaimed body."

Joseph Ryan made headlines in July after court documents emerged revealing that Tylee told a therapist that she was sexually abused by her father in 2008. The claim was later recanted.

Cushing said Vallow and Ryan were fighting over custody at the time, and she believes the accusations against her brother were fabricated by Vallow in order to win the legal dispute. 

Lori Vallow, 46, faces multiple charges, including two felony counts of desertion and nonsupport of children, according to a criminal complaint filed with an Idaho court. Credit: Madison County Sheriff's Offic

Lori Vallow, 46, faces multiple charges, including two felony counts of desertion and nonsupport of children, according to a criminal complaint filed with an Idaho court. Credit: Madison County Sheriff's Offic

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"That's always a tough question because I wasn't there," Cushing said, "but based on what I've read from all of these court documents and what I witnessed from Lori when I was out in Pheonix in 2013, the way she spoke about this, I mean, she had no filter. She talked about it in front of Tylee.

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"And it was like she was like manic about it," she added. "And she just didn't treat it with any of ... the appropriate parental protocols that you would expect if you really thought your child was molested. So, all of those things combined indicate to me that this was more the result of Lori's machinations in order to win custody and to completely edge Joe out of Tylee's life."

Vallow remains jailed in Idaho along with her fifth husband, Chad Daybell, on conspiracy charges related to allegedly hiding the remains of Tylee and 7-year-old Joshua "JJ" Vallow. The children's bodies were found on Daybell's property in June. 

To watch the full series of "A Lori Vallow Investigation With Nancy Grace," visit Fox Nation and join today.

Fox News' Louis Casiano contributed to this report.