Family Killer Chris Watts' 'Twisted' Sexual Relationship With Mistress Led Him to Murder Wife and Kids, Reveals Pen Pal

Chris Watts' killed his whole family because of his sexual obsession with an ex-mistress, according to his pen pal.

Watts, who murdered his pregnant wife, Shanann, and their two daughters, Bella and Celeste, in August 2018, told pen pal Cheryln Cadle that he couldn't get enough of his lover at the time, Nichol Kessinger.

"A lot of it is stuff I just won't repeat," Cheryln, 72, said to an outlet on March 8. "But his relationship with her was very sexual, very twisted, very mixed up. And that's part of why I believe he did what he did."

While Cheryln, who published a best-selling book about Watts' confessions in 2019, wouldn't go into detail, she revealed Chris would tell her "a lot of things you wouldn't tell your mother."

Per the outlet, the Colorado dad liked that Nichol would send him nude photos and engage in unspecified "dark" sexual acts that his wife wouldn't.

"He was obsessed by NK," the true crime author said. "He talked about her all the time."

Cheryln, a self-described "mother figure" to Chris, added that he must have "some sort of fetish" to want to tell her about the things he did with Nichol.

Chris wrote in one letter to Cheryln, "If I had not met Nikki, I would never have killed my family. All I could feel was now I was free to be with Nikki. Feelings of my love for her was overcoming me. I felt no remorse."

"The darkness inside of me had won," he continued. "It was still in me, though, I thought maybe permanently. I felt evil, swallowed up by this thing inside of me. I felt like I could kill anything and be justified for doing it."

After lying to police initially, Chris eventually admitted murdering his wife and children and pleaded guilty to avoid the death penalty. He was sentenced to five life sentences without the possibility of parole.

Cheryln divulged that she first wrote to the former oil field operator in February 2019, explaining that she "thought he was totally guilty."

"I didn't ever expect him to write back," the grandmother admitted. But he did, and she later visited him Dodge Correctional Institution, maximum-security prison in Waupun, Wis.

"I tried not to judge him — at least not to his face, and I listened to whatever it was that he had to say," she shared. "So he felt he could confide in me."

Cheryln also spilled that Chris "confessed not once, but repeatedly" in their exchanges.

"He revisited details. He contradicted himself. He rationalized, minimized, and occasionally revealed more than he intended to," she relayed, adding that he only grieved "being perceived as a good husband, a good father, a good man."