What will you do if you discover months to your wedding, that your fiancee is your half-brother and he's known for a year and hid it from you?

According to this Raddit user oopcest, they had an "instant connection"  and fell head over heels in love without knowing they were blood.
In a thread titled ‘I found out yesterday that my fiancé and I are related. He’s known for a year’, Reddit user “oopcest” sets the scene for how this 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.”

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The Reddit user told how when they first started dating, there was an instant connection. Picture posed by models

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 fiancé’s family is the complete opposite.
She explained: “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 (mother-in-law) mentioned that my fiancé’s dad is actually his stepdad.

The bizarre scenario is similar to an Emmerdale storyline in 2010 where Maisie Wylde fell in love with her half-sibling Ryan Lamb

“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 fiancé 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 child-free, 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?”

The woman’s fellow Reddit users 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 Redditors suggested her partner’s lying was a bigger concern than them being related.
One wrote: “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.”

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But the couple decided to tell their family anyway, and it did not go well.
She recalled: “We decided to tell his mum 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.
source: sun uk