IT all started with a kiss whilst watching the movies with their pals.
At least, this is how one woman claims she started a sexual relationship with her brother when she was 14 and he - 16.
According to the woman, who is now in her late 30s, she had always found her older brother attractive both physically and emotionally and suspected that he was attracted to her ''in the same way''.
It wasn't until both the kids, who come from a family-of-five, had reached teenage years that they decided to explore their twisted fantasies together - and it was all because of a movie night with their mates.
The anonymous woman, who gave her sibling a fake name, Carl, explained that she and her brother were watching a film whilst her friend and her boyfriend were passionately making out in the background.
''At some point Carl pointed at them and said something like, 'Wow, do they even care that we're right here?' and I just laughed and said, ''What, you've never made out in front of people before?'
read more on relationships
''He said, 'No,' and I said, 'Want to try?'''
The woman, who shared the sick romance story on Reddit, said she felt ''the stars were aligned correctly that night'' and she ''finally had the confidence to go for it''.
Five minutes later, she recalled in the post, she found herself ''on his lap making out with him''.
Despite what they had just witnessed, the other couple in the room didn't say much and the subject was ''never'' brought up afterwards.
Most read in Fabulous
However, the kiss soon allegedly turned into having oral sex - which the woman claimed she was the one to suggest - and was then followed by trying the ''real thing''.
Although at first the anonymous Redditor said she felt that having sex was ''going too far'', her older brother convinced her otherwise - and she gave in, after experiencing twisted sexual fantasies about him before.
''In those fantasies, I would try to conjure up an image of a man who was strong, handsome and who loved me deeply for who i was and would not hurt me in any way.
''His face always came up and I didn't see anything wrong with that.''
The social media user, who hadn't had a sexual relationship with anyone prior to sleeping with her brother, said it ''felt perfect''.
''I was positive from the beginning that he genuinely loved me. With other guys there's always that, 'What if he just wants to get into my pants?' thought.
''With Carl, I knew he truly loved me if I had sex with him or not.''
For a brief moment the young woman, whose alleged story has left many ''disgusted'', also wanted to have a baby with her brother - however, she ''snapped out of it pretty quick''.
Responding to the horrified readers, she confessed: ''I'll never understand why so many people think incest is wrong.''
The sexual relationship continued for several years after they first slept together that night and the siblings would pop into the ''kids' room'' when their parents had gone out for the day.
The Law on Incest in the UK
INCEST refers to sexual activity between close family members, such as siblings, parents and children, or grandparents and grandchildren.
- Criminal Offence: Engaging in sexual activity with a close family member is illegal.
- Close Family Members: Includes siblings (full or half), parents, children, grandparents, and grandchildren.
- Penalties: Those found guilty of incest can face significant legal consequences, including imprisonment.
- Protection and Welfare: The law aims to protect individuals and maintain the integrity of family relationships.
- Consent Irrelevant: Even if both parties consent, it is still considered a criminal offence.
Although the pair were never caught by their mum, dad or little sister, there was a ''close call'' shortly after the then-teenager had started college when he roommate allegedly saw them having sex one night.
To avoid any questions and drama, she quickly made up a lie and told her pal that her brother was, in fact, her boyfriend.
''But a few days later my parents visited with my brother and my roommate referred to him as being my boyfriend; my mum was really confused, as was my roommate, but my dad just laughed and said that it sounded like my 'boyfriend' was a handsome guy (my dad looks a LOT like my brother.
''My dad was laughing because he assumed I was dating someone who looked like my brother - hence my roommate's 'mistake'.''
She went on: ''As for who was more into it? That depends. At first it was me, but soon it was him, then vice versa, etc.
''He was the most generous lover I've ever had and I'd like to think I was equally generous but there were definitely times when one of us just wasn't into it or wanted to stop it completely.''
But the sick love story eventually came to an end when her brother ''fell in love with someone else and got married''.
''No, I'm not bitter. Part of me does miss being with him, still, and the way he ended was pretty abrupt (basically, he said to me, out of nowhere, that he was engaged now and couldn't be with me anymore.
''I asked him if he loved her and he said he did. That was that.''
The woman, who said his wife doesn't suspect anything, claimed that she gets along with his brother's new love.
''Initially I was sort of jealous but deep down I knew it wasn't like Carl and I could ever get married and have a family or anything.
''But the jealousy was there, it was real, especially at the wedding. I never took it out on her, though. She's one of the sweetest people I've ever met.''
Although she hasn't opened up her new love life since, the Redditor revealed that Carl and her wife are currently expecting a baby.
READ MORE SUN STORIES
''Carl was easily the most amazing lover I ever had. I know he's going to read this comment, and guess what? I don't care.
''Because it's totally true. He was amazing. And I don't regret any moment of what we did together, I truly don't.''