Hugh Hefner's Ex Karissa Shannon Says She Aborted the 84-Year-Old's Baby, Claims Sex Was 'Like Rape'

"Playboy Twins" Karissa and Kristina Shannon were two of Hugh Hefner's last girlfriends as the aging mogul enjoyed his final stretch of international fame and public polyamory.

Thirteen years after the end of their 18-month relationship, which was chronicled for E!'s reality series The Girls Next Door, the sisters do not look back on their time with Hefner fondly. "It just started becoming a job right away," Karissa said on Monday night's episode of A&E's docuseries Secrets of Playboy.

During this week's episode, "Behind The Girls Next Door," the Shannons detail the lows of the affair, the alienation and violation they felt from their much-older boyfriend, as well as the emotional processing they've had to undertake as a result of a sexual arrangement that they say still makes it hard for them to "emotionally connect" with others.

(PEOPLE has not independently verified the allegations reported in the episode, and A&E advises viewers, "The vast majority of allegations have not been the subject of criminal investigations or charges, and they do not constitute proof of guilt.")

RELATED: Secrets of Playboy: Breaking Down the A&E Docuseries' Biggest Bombshells About Hugh Hefner's Empire

Michael Bezjian/WireImage Hugh Hefner and Karissa Shannon

BECOMING PLAYMATES

Now 32, the Shannon twins were 18 years old when they met Hefner, then 83. They'd been raised by their grandmother in Clearwater, Florida, and were working at a Hooters-style restaurant when they were scouted to do a test shoot for Playboy.

Their photos immediately captured the attention of Hefner and his then-No. 1 girlfriend Holly Madison, who was overseeing the search for Playboy's 55th Anniversary Playmate on Girls Next Door.

Though they didn't win the contest, they were named the July and August 2009 Playmates — and received an "old-school" letter from Hefner inviting them to move into the Playboy Mansion with him.

They claim they didn't realize at the time that the invitation came with strings. As Karissa said, "Hell no, you don't think an 80-year-old man is sleeping with [all] these women."

RELATED: Holly Madison Claims Women Felt Pressure to Sleep with Hugh Hefner to Be Playmate of the Year

Denise Truscello/WireImage Karissa Shannon, Kristina Shannon, Kendra Wilkinson, Bridget Marquardt, Hugh Hefner, Holly Madison and Crystal Harrsi

BECOMING GIRLFRIENDS

A few months after they relocated to Los Angeles, the twins celebrated their 19th birthday. "That was the night that we realized," starts Karissa, with Kristina finishing the sentence: "What we got ourselves into."

According to the twins, Kendra Wilkinson (another former Girls Next Door star) invited them to smoke marijuana in Hefner's bedroom, but when the twins got there, Wilkinson and Madison ghosted them.

And though Hefner himself seemed "super nervous," he pulled a familiar move and offered the twins — who'd already been drinking, despite being underage — a pill to ease their nerves.

According to Karissa, they immediately felt "really f---ed up … the most inebriated we've ever been."

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She claimed Hefner began "pulling our heads down, like a very hard pull, down to his penis so that we would give him oral sex."

Kristina said, "We had never done a threesome together before, we would never want to."

Noted Karissa, "And that was our 19th birthday. You're never going to forget that."

She continued, "He didn't even finish. Just imagine this, just his old hand kind of shakes [as he's] touching your boob. It's like you're having sex with your grandpa. And he laid there, looking up, and he was like, 'My babies, my babies. You love me.' "

The twins waited for Hefner to fall asleep. Once he did, "We ran down the hall to the spare bedroom we were staying in. We hit the shower, steaming hot. Our skin was red from just trying to, like, sterilize," said Karissa.

Kristina added, "After that night, I didn't feel like my body was mine anymore. Like, I felt used, disgusted."

Remembered Karissa, "Both of us said, 'He's going straight to Hell.' "

And yet, with their centerfold hanging in the balance, the women said they felt like "there was no going back, we couldn't leave."

RELATED: How Young Women 'Signed Their Life Away Forever' to Hugh Hefner

RICH SCHMITT/AFP/Getty Hugh Hefner

As the months wore on, the twins recognized Hefner's "seduction" ritual worked like clockwork — when the clock struck midnight, he'd invite any women in his house up to his bedroom. So they said they developed a habit of quelling their anxiety about that night's sexual encounters by self-medicating with alcohol.

"Dinner started at 5 every Friday, Saturday and Sunday," recalled Kristina. "And so, at dinner is when we would start drinking. They had open bar, so we'd start drinking just in case Hef wanted to apply that pressure."

According to Karissa, "We were drunk every night... Every night — to try to deal with him."

Eventually, the lifestyle at the Mansion caught up with them.

"There was at one point an STD that went around," claimed Kristina. "We caught chlamydia. I remember going down to Mary O'Connor's office — his assistance slash, I'd say, house mom for us — and she's like 'Well that's what happens when you're sexually active.'"

She continued, "We freaked out! When she said, 'STDs are normal when you're sexually active,' we're like, 'Everyone's out of their mind here.'"

The twins vowed to "never have sex with [Hef] again. That was it."

RELATED: Secrets of Playboy: Inside Hugh Hefner's 'Circus' of Sexual Debauchery

David Livingston/Getty Karissa Shannon, Kristina Shannon and Hugh Hefner

BECOMING PREGNANT

For the most part, they succeeded in keeping to themselves, but Hefner eventually caught on and "told us that if we loved him and we wanted to be his girlfriends, then we have to have sexual encounters with him," according to Karissa.

"The problem is, Hef doesn't like to use protection," said Kristina. "From the butlers, we'd just order a big bowl and we'd put hot water in it, then we'd put rags in it. So whoever was having intercourse with him, when they were finished, they can wipe him off. And then the other girl could do it."

So, despite the fact they claim to have had sex with Hefner only twice more during the course of their relationship, Karissa eventually discovered she was pregnant with Hefner's child when she took a blood test in preparation for plastic surgery.

"I got a call saying, 'Hey, you're pregnant' [and] I freaked," she said. "I'm like, 'Who else knows about this? … Don't call Mary, don't call Hef, don't call anyone, I don't want anyone knowing.' "

At the time, Karissa said she "didn't think it was possible" to conceive a baby with Hefner, who was 84 at the time. After all, Madison had publicly struggled to become a mom toward the end of her relationship with Hefner. But, Karissa noted, "We were about the youngest girlfriends he had had — it was the end of [when I was] 19, I was getting ready to turn 20."

She instantly knew she wouldn't keep the baby. What's more, "I didn't want him to know that I was pregnant. I didn't want him to want me to have it. I didn't want to be stuck even more inside that bubble. I think it's a way for him to control me even more, have me on a leash," she said.

"I felt disgusted with my body," she continued. "I felt like there was something like an alien inside me. I was grossed out. I just wanted to get it over with."

The twins cried as they recalled the secret visit to the abortion clinic they planned, with the most devastating decision of all falling to Kristina, who realized she couldn't accompany Karissa to her appointment for fear of attracting paparazzi attention.

When they returned to the house after the procedure (carrying thong underwear they had bought to support the ruse that they'd just gone shopping), Karissa and Kristina were met with a camera crew and told they needed to film their footage for the show's opening theme song. Karissa said she felt so awful, Kristina had to act as her body double.

Despite the trauma, though, Karissa affirmed that she "100 percent" made the right decision.

"Every time I've done it with him, it's assault," she said of sex with Hefner. "To me, it's like rape. He used control mechanisms completely through everything, so I'm happy that I had the abortion."

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Matt Winkelmeyer/Getty Kristina and Karissa Shannon

BECOMING EXES

The Girls Next Door aired its final episode on Aug. 8, 2010. Six months later, the twins told Hefner they wanted to leave the Mansion. They said he tried to devise a compromise where he'd cut their allowance of $1,000 per week in half if they stuck around, living in the "Bunny House" outside the main Mansion, but the arrangement was short-lived. They eventually parted ways while Hefner went on to marry their Girls Next Door costar Crystal Harris Hefner, his third and final wife.

Even though more than a decade has passed since they left Hefner, the sisters say they're "still dealing" with the aftermath of the relationship, including a PTSD diagnosis.

"He has so much power. It's like you're in a cult," said Kristina. "You lose yourself being there, all that innocence about us [was lost]. It's hard, it's like being in prison and someone breaking you in solitary confinement. You're just broken."

Said Karissa, "I don't think that that part is ever gonna go away, that part of us that was taken."

RELATED: Holly Madison Says the Playboy Mansion Was 'Cult-Like': 'We Were All Gaslit'

In a statement released just before the docuseries' premiere, Playboy's current leadership wrote, "We trust and validate women and their stories, and we strongly support the individuals who have come forward to share their experiences."

The statement also noted, "Today's Playboy is not Hugh Hefner's Playboy."

Secrets of Playboy airs Mondays at 9 p.m. ET on A&E.

If you or someone you know has been sexually assaulted, please contact the National Sexual Assault Hotline at 1-800-656-HOPE (4673) or go to rainn.org.