Until she was 40, Melissa* thought she was an only child. For the first decade of her life, she grew up happily in a suburban, upper-middle class area of the Great Lakes. Then, her father committed suicide, and soon after, she says, her mother's mental health began to decline.

"I had to be her caretaker," Melissa says, sharing about her mother shoplifting, peeing in public, and "other weird behaviors." Their home life got difficult. Her mother's boyfriends often lived with them, and she let her teenage daughter have guys stay overnight. When Melissa was 14, her much-older lover was allowed to move in for a time too. There were no boundaries, she says of her mother, who died several years ago. "She spoiled me rotten and let me do anything, probably because she felt guilty for hiding who I really was."

A Shocking Revelation

In January 2015, a Facebook friend request came from Chris*, a man she didn't know — and her world shifted drastically again. "When I messaged to ask how I knew him, he said, 'If I really told you, you wouldn't believe it,'" she says. "I pushed, and he said, 'Your dad was not your dad. Your mom lied to you your whole life about who your father was.'" Chris claimed to be the stepson of Melissa's real biological father, who had recently died. He said he grew up knowing his stepfather had a secret child out there, and even tried to contact Melissa years before, but her mother always intervened. "He knew all this information about me," she says. "Of course, I was flipping out."

She asked to meet Chris in person. Though she was raised to believe her mother's husband was her father, Melissa learned that four decades before, her mother had an affair and became pregnant with the other man's child.

The news got even more startling: Before his affair with Melissa's mother and eventual marriage to Chris' mother, her biological father was married a first time — and Melissa had several half-siblings. "It was all so crazy. I was dumbfounded," she says. "My life was just exploding."

After their meeting, Chris, the stepbrother, gave her contact information to Brian*, one of her half-siblings. And Brian, 45, immediately reached out to her on Facebook with a simple note: "Well, I guess I'm your brother." He says he asked if she was doing OK with all the news. "I knew it was a huge, life-changing thing for her to find out."

A flurry of messages led to a phone call.

"That's where things started getting a little bit weird," says Melissa. She remembers having an immediate and intense reaction to hearing Brian's voice. "I don't really know how to describe the feeling, but I was really attracted to it."

I thought, 'There is something wrong with me. Something isn't right.'

Later that night, the pair separately scrolled through each other's photos on Facebook. As she looked at the images of Brian's life — as a musician, friend, and husband — unexpected feelings stirred. "I was confused. I was attracted to him. Then in bed, I started having actual sexual fantasies," Melissa concedes. I thought, 'There is something wrong with me. Something isn't right.'

Two hours away, in the home he shared with his wife, Brian experienced the same thing. "I was mourning my father, and seeing her was like new life, like I'm so blessed to have a sister," he says. But, he admits, her photos made him feel "very turned on ... I thought, 'I must be a sick and terrible human being.'"

Desperate to Meet

Two days later, Melissa drove two hours during a Monday night Midwestern snowfall to meet her brother. When she saw him standing in the frigid air outside his office building, she felt a connection that was instantaneous and electric.

"It was love at first sight, absolutely the craziest thing I have ever experienced," Melissa says. "The sexual force was like I was levitating off the earth. Your body instantly craves the other person."

The feeling was mutual: The pair shyly hugged and they had trouble looking at each other, in part because it was like gazing in a mirror, they looked so similar. "It was trippy, like seeing yourself in the opposite form," Brian says. "Everything inside you is just vibrating. Your cells know that this is your person."

They drove together to a nearby bar, and on the way, Brian grabbed Melissa's hand and found himself telling her everything. "He starts divulging these deep, dark secrets. Things he's never told anyone," she says. "I'm doing the same. We're talking nonstop, insane and enthralled."

After a quick drink, they got back in the car and were quickly tearing at each other's clothes like teenagers. "We couldn't keep our hands off each other," Melissa recounts. "It was primal, but we were also scared, like, 'What is wrong with us?'"

There must be some natural explanation for these feelings, Brian remembers thinking. And according to them, there is. The half-siblings say they are prime examples of genetic sexual attraction (GSA). The term was coined by in the 1980s after she experienced an attraction to the adult son she had placed for adoption as an infant. (She later started a support group for other families.) While the American Psychological Association does not use the term, GSA is what it sounds like: a phenomenon that occurs when two family members, who were separated early in life, eventually meet and experience an intense sexual attraction to each other — though not all act on it.

The Last Taboo

On the way home, Melissa called a friend to explain what happened. The friend immediately inundated her with articles on GSA. "I felt a little bit better seeing that this is out there and I wasn't crazy," Melissa says. And while they didn't want to resist their overwhelming sexual attraction to each other, the couple desperately did want to understand why they were experiencing it. Over the past 10 months, they've read as many articles on the condition as possible and even saw a psychologist.

Social scientists and psychologists have long researched how societies' prohibition against incest evolved: It's essentially nature's way of protecting humans from passing along the genetic mutations and disease risks that happen more commonly with close relatives, explains Dr. Debra Lieberman, a professor of Psychology at the University of Miami. The dominant theory, first proposed by Finnish social scientist Edward Westermark, is that people become desensitized to those they are raised alongside.

"Westermarck's hypothesis and my research have shown that siblings use clues like living under the same roof and being cared for the same parents to develop a sexual aversion," Lieberman says. "But if you don't grow up together, no aversion naturally develops."

She says GSA is a "misnomer," though, because attraction to relatives usually requires shared genes and not being raised together — just because you're genetically related, it doesn't mean it will happen. This is why sexual attraction is occasionally reported in adoption reunions, some claim in as many as 50 percent of cases.

The flip side is something Lieberman calls her "template hypothesis." All people form a template for the world based on the people and their surroundings during development: what men and women look like, what their roles are, etc. Then, they seek that out in a mate. This is common for non-related couples, too, psychologist and sex expert Isadora Alman notes.

"Many couples experience the feeling of being instantly attracted to someone that is familiar in some way, whether it's a physical reminder of someone beloved or something else they can't put their finger on," Alman says. "Love at first sight is a real phenomenon."

But it's been suggested that this feeling is even stronger for consanguineous (aka related) couples, especially those who don't develop the ick factor from growing up together. Why? "Genes tend to shape our preferences, talents, and attitudes — and familiarity creates comfort, so we look for someone similar," Lieberman says. "For siblings, this drives an enhanced sexual attraction." Which is exactly what happened to Melissa and Brian.

Everything inside you is just vibrating. Your cells know that this is YOUR person.

Turning Their Lives Upside Down

Two weeks after they met, Brian left his wife. "Melissa wasn't the reason I left, but she was the catalyst. My marriage had been over for a while, I just didn't know how to get out of it." He hasn't told his ex — or his mother and siblings — about the sexual part of his relationship with Melissa, but his grown-up daughter from another marriage knows. His daughter "gets that I'm weird," Brian says, describing himself as artistic. She was initially shocked, but "as she thought about it, she knows that my sister can heal me in ways that other people can't," Brian says. "She's on board."

Melissa hasn't told her family either. She still lives with her two teenage daughters and her husband, who she calls "an open-minded guy," adding that in nearly two decades together she's been in multiple other relationships. "He's allowed it because he knows who I am and my upbringing." They haven't been intimate in five or six years, but are committed to co-parenting.

Even though her kids don't know everything, they're aware she has some sort of relationship with Brian, who they've met once. She sleeps over at his house every Saturday. "They're not dumb, and obviously, that's going to look weird," she admits. The girls are angry or upset when she returns. "My daughters view him as an infiltrator, as some guy who fell from the sky, and made their mother go nuts and be gone all the time," Melissa says. "There's a lot of animosity in my house. I'm living a double life."

But divorce is not an option right now. Melissa plans to get her daughters through the rest of their childhood in as stable and consistent an environment as possible. "But believe me, I want to leave," she says. "I struggle every day because my heart is with him. That's the most difficult part for me."

Still, she has told a couple of her closest confidants. Kimberly*, who's been her friend for more than 15 years, counseled Melissa to slow down when she first met Brian. "The emotions were running high," Kimberly recalls. "Every time she saw him, it was just more intense. When she told me they were lovers, I was quiet and just listened to her talk about him."

Slowly, she started to accept her friend's new "brother-lover," as she jokingly calls him to Melissa — even joining them for drinks a couple times. "When I met him, it all clicked," Kimberly says. "I don't understand it, but I can see their connection. It's magnetic, like gravity."

Foundation for Romance

Beyond their physical attraction, Melissa and Brian bond over the same commonalities other couples do: shared tastes in music, similar childhood experiences, a fondness for tattoos. "You wouldn't think that everything would line up, but it did," Brian says. "There's even molestation in both of our backgrounds — and at the same age, by the same [kind of] people who were at the same age."

Melissa adds that they lived parallel lives: "We were often doing the same types of behaviors, experiencing the same things, just not together. It's obviously a genetic thing."

Science supports that. "By virtue of sharing genes, they also share a lot of predilections, more so than two people plucked at random," says Lieberman, who has extensively researched the role of kinship in sexuality. "Genes tend to shape our preferences for kinds of food, music, sleeping patterns, even exercise."

We have an innate trust and no boundaries because we're family. My brother is never going to hurt me.

They claim their sexual and emotional connection is exceptional. "We have an innate trust and no boundaries with each other because we're family," Melissa explains. "When you get into a relationship with someone else, they're a stranger to you. Trust takes a long time to build. But because this is my brother, he's never going to do anything to hurt me."

Their unusual circumstances have created a perfect storm, an ideal mix that most people don't get to experience. They describe levels of intimacy and exploration, of freedom and kink, of sacredness and naturalness. Tantric and bondage are mentioned. To them, it's more than romance: Their relationship covers all the forms of love the ancient Greeks espoused — friendship, sex, siblinghood, and self-sacrifice.

"He's able to be my father, my brother, my lover, my best friend — all these roles that others have never filled," says Melissa. "I have everything in one human."

"All I care about is her happiness," agrees Brian. "And from the moment we met, I've known exactly what she lacks and what she needs. And she knows exactly what I need innately, naturally."

Planning for a Future

All states in the U.S. have laws prohibiting marriage or sexual intercourse between first-degree relatives. In their state, it's a felony that's punishable by life in prison. Not only do Melissa and Brian feel their love shouldn't be forbidden, they also say they're part of a growing segment of society: As infant adoption and fertility treatments involving sperm, egg, and embryo donation increase, so will the numbers of people walking around who are unknowingly genetically related.

"When people like us meet, all of your body vibrates knowing this is your kin, your genes. It's a very interesting phenomenon that's not studied in this world," Brian says. "If we don't start studying it more — or accepting it — people will end up in jail."

Though Kimberly is not opposed to their relationship — "They're both consenting adults," she says — Melissa's friend is concerned about how finding out will impact their kids. Alman adds that contempt and rejection are the greatest consequence for most consanguineous couples: "That happens anytime someone breaks a taboo, and this one is a strong one," she says. "Any couple that does this has to be prepared to lose the love and respect and company of their family members."

Regardless of the risks, the half-siblings plan to eventually live together — and officially marry. And they can because of a legal loophole: Melissa's childhood father is listed on her birth certificate, not their shared biological father. "Obviously, it's still illegal. But we can hide and do that." So after her kids are raised and their divorces are finalized, they plan to live happily ever after, she says. "It's just not going to be for a number of years, unfortunately."

Until then, they will keep sharing their Saturday nights and balancing the challenging dynamics of a relationship under-cover. It's well worth it to them.

"I don't feel like we're more special than anyone else, but to receive this intense kind of love is a gift," Brian says. "Few human beings get to experience something at this level. And it's not a taboo. It's nothing wrong. This just feels like love, perfect love."

*Names have been changed to protect anonymity.

Asher Fogle Writer When she’s not hunting for compelling personal stories or justifying her love for dessert, Asher can likely be found watching early-2000s TV on Netflix with her husband.

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