ARE you sitting down? Good.
You're going to need some support while you read this woman's account of how she found out her fiance, the man she describes as her "soulmate", is actually her half brother.
In a thread titled, "I found out yesterday that my fiance and I are related. He's known for a year", Reddit user "oopcest" sets the scene for how this could have possibly happened.
She writes the pair "had an instant connection" upon meeting and soon fell head over heels for each other.
"It was a big deal for both of us," she wrote. "We're both nerds ... and our social circles are pretty small. Both of us have trouble getting out there and socialising. We're more the type to keep our heads down. It was only my second serious relationship and his first.
"After a year of dating, we got engaged. We finally moved in with one another a month ago and our wedding is in six weeks. Beyond the normal little domestic naggings, things have been perfect. He's my soulmate. I don't know what I'd do without him."
Their families are quite different. Hers is really small and her father was never involved in her life.
"I was raised by a single mother and her parents. It was dysfunctional; but not as bad as it could have been. No one got molested or anything. There was just a lot of fighting on top of the absentee dad stuff," she wrote.
Her fiance's family is the complete opposite.
"They're pretty much perfect. His mum and dad are great and the most giving people I know. His sister has become one of my dearest friends. They even sit down with each other for Sunday dinners. Who does that? I've always been in awe of them.
"I always thought they were perfect, so it came as a shock to me that - while working on wedding invitations - my future MIL mentioned that my fiance's dad is actually his stepdad.
"I asked to see a picture of his real dad and I nearly passed out when my MIL showed me a pic of my dad."
Cue life breakdown.
"I don't know how I kept from screaming and stayed conscious. I excused myself from the room and promptly threw up. I'm pretty sure she thinks I'm pregnant now; which is just a whole other can of worms unleashed," she wrote.
"I got home and confronted my fiance about it. I was crying. I was screaming. He just sat there, fidgeting. Eventually, he admitted that he's known for a year but didn't want to lose me. Since we always planned to be childfree, he didn't see the problem with just keeping it from me.
"I'm betrayed. I'm disgusted. I'm hurt. I'm ashamed. I'm heartbroken. I don't know what to do. I've invested so much money into this wedding and much of it is non-refundable. On top of that, I don't know how I'm going to explain this to my family and friends. Worse yet, I love him. I know we can't be together; but until yesterday, I thought we'd grow old together. What do I do? What the f*** do I do?"
Her fellow Redditors were quick to offer their support and encouraged her to be honest with her family. Others shared their own experiences with Genetic Sexual Attraction (GSA), the term for incest between close relatives.
GSA is rare but it known to occur between genetic relatives who meet as adults, often through adoption, and have no idea that they are related. It is often referred to as "accidental incest".
Many commenters suggested her partner's lying was a bigger concern than them being related.
"A lie - and it is a lie by omission - that big is a conscious choice, and the fact that he was able to hold onto it for so long with no apparent major qualms is really worrisome. That kind of thing is a red flag in any type of relationship," one commenter wrote.
But the couple decided to tell their family anyway, and it did not go well.
"We decided to tell his mom and stepdad. It went horribly. They disowned him and cut him off; which is a huge f***ing problem since they were paying for a portion of our apartment.
"The way they reacted was just a taste of how we feel others will respond, so we've decided to break up. However, before we cancel our wedding plans outright, we are going to speak to our father and take a DNA test. Thank you to everyone for their support and kindness ... I just wish things had had a more positive end."
The woman thanked the Reddit community for their support and their advice, though many also encouraged the couple to seek professional help.
"The majority of you seem to be totally cool with the idea of brother-sister incest. I know the internet is kind of a depraved place; but I wasn't expecting that AT ALL," she wrote.
"Unfortunately, I don't think that same attitude would be mirrored in the offline world. And, even if it was, I'm not sure I can go through life as the girl who married her brother."
Read the comments thread here.