A long-lost brother and sister talk about their romantic relationship.

Image: iStock.

Most couples have hurdles to overcome but Melissa and Brian’s have experienced more than most – the pair are half-siblings who met in their 40s and quickly fell in love.

In an interview with Good Housekeeping, the US couple (who’s names have been changed) spoke about their undeniable connection and the everyday challenges they experience with their relationship.

It all started when only-child Melissa received a Facebook friendship request from someone who claimed to be the stepson of her biological father, who had recently passed away. After meeting in person, she learnt that not only was her mother’s husband not her father as she’d been brought up to believe, but that she also had several half siblings.

After connecting with one of her half-brothers Brian on Facebook, the pair were soon exchanging hundreds of messages which led to a phone call and the start of a deep connection.

That night, both recall looking at Facebook photos of each other and having confused feelings about each other.

“I was confused. I was attracted to him. Then in bed, I started having actual sexual fantasies. I thought, ‘There is something wrong with me. Something isn’t right,'” said Melissa.

For Brian, it was even more conflicting: “I was mourning my father, and seeing her was like new life, like I’m so blessed to have a sister… [but the photos of her] made me feel very turned on … I thought, ‘I must be a sick and terrible human being’. (Watch relationship expert Dr Nikki Goldstein answer the most common questions she gets asked about relationships. Post continues after video.)

Two days later when they met in person for the first time, the connection was “electric”.

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

After a drink in a bar and sharing their history and secrets, the pair found themselves in the car “tearing each other’s clothes off like teenagers”, unable to keep their hands off each other.

“It was primal, but we were also scared, like ‘What is wrong with us?,” said Melissa. (Post continues after gallery.)

Still together after 10 months, Brian left his wife two weeks after their first meeting while Melissa remains living with her two teenage daughters and “open-minded” husband who allows her to be in multiple relationships. She refuses to divorce her husband as she wants to keep her daughters’ childhood as stable and consistent as possible.

“But believe me, I want to leave. I struggle every day because my heart is with him. That’s the most difficult part for me,” she admits.

However neither have told anyone of the sexual nature of their relationship aside from one of Brian’s daughters.

“[She] gets that I’m weird. [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. She’s on board,” says Brian.

Having done hours of research and even seen a psychologist trying to come to terms with their feelings for each other, the couple argue they are an example of Genetic Sexual Attraction (GSA), a term used to describe a phenomenon where two family members who have been separated early in life meet when they’re older and experience an intense sexual attraction, although not all follow through.

According to a theory first proposed by Finnish social scientist Edward Westermark, people become desensitised to those they are raised alongside and develop a sexual aversion, but if you don't grow up together no natural aversion develops.

Although it's against the law to marry or have sexual intercourse with first-degree relatives in all US states, Melissa and Brian hope to have their "happily ever after" in the future and believe that their love shouldn't be taboo.

"Obviously, it's still illegal. But we can hide and do that. It's just not going to be for a number of years, unfortunately," says Melissa.

"I don't feel like we're more special than anyone else but to receive this intense kind of love is a gift. 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," says Brian.

Have you heard of GSA before?