When a family decided to take DNA tests "for fun", the mum never predicted the bombshell that would be revealed as a result - their youngest son was, in fact, a stranger's.
Donna Johnson, 47, and her husband Vanner, 47, took DNA tests along with their two boys - Vanner Jr, 18, and Tim, 12. She explained they took the test "for fun" in order to discover more about their heritage.
But when they got the results back, Donna was shocked. "Reading the DNA tests results online, I figured there had been a mistake," she wrote in The US Sun.
Vanner was the father of their eldest son, but the results said the father of the youngest was unknown. Donna tried to wrap her head around what the results meant, when she had a moment of "sickening clarity".
She realised there must have been a mix up at the IVF clinic.
Vanner and Donna, from Salt Lake City, Utah, met in high school and got married in 2003. The couple had their first son, Vanner Jr, and were excited to have another child.
But hernia problems and surgery caused damage which made it impossible for the pair to conceive naturally. So they had their first round of IVF in 2007, using Donna's eggs and Vanner's sperm.
The first round failed, but that same summer they tried again with more success. When their son, Tim, was born in August 2008 Donna said it "felt like a miracle".
The boys looked different, but Donna brushed it off as many siblings look different. Vanner Jr was described as having his dad's blue eyes and fair hair, while Tim had Donna's dark hair and was sportier.
As home DNA testing has become more available, the family decided to do their own test to learn more about where they come from. Six weeks later, the results came back and changed their lives forever.
Donna said their denial quickly gave way to fear, with the family wondering who Tim's biological dad could be, and whether he could be taken away from them. Thankfully a lawyer was able to reassure the couple they'd remain Tim's legal parents.
But for Donna, it was difficult to watch Vanner come to terms with the fact that Tim wasn't his own biological child. She said he didn't act any different around Tim, but she could tell he was in shock.
As the husband and wife came to terms with the earth-shattering news, Donna said she sank into depression and struggled to focus at work as a teacher.
A counsellor helped the couple work through the revelation, Donna said they decided to tell Tim the truth when he was 12, as they thought it would be worse if he found out as an adult.
So, in October 2020, Vanner took Tim out for ice cream to break the news that he wasn't his biological dad. When they got back, Donna wrapped her youngest up in a huge hug, telling him how much they loved him.
She said he was very quiet, but said he loved them too. Vanner recounted what happened over ice cream to Donna, telling her that Tim had taken a few seconds to process the news before making a comment about wishing he knew what he would have looked like with Vanner's genes.
Donna explained that Tim handled it with "such maturity" as did his older brother. A few weeks later, Tim told his parents he wanted to track down his biological father.
As much as Donna and Vanner respected his decision, they were worried, as any parent would be, about what might happen. So they used another DNA test from a different company, which helped them track down a woman they thought could be Tim's biological aunt.
After some more investigating, they found a blog written by the woman's brother, a man called Devin McNeil who lived in Colorado, eight hours from the family. They found his number, but knew that calling it would change all their lives.
However, Donna and Vanner respected Tim's wishes and called Devin in March 2021. Vanner and Devin spoke on the phone, and though Devin, 47, had been sceptical, he had agreed to do a DNA test.
Donna said they talked on FaceTime with Devin and his wife Kelly, 46, which was anxiety-inducing. But she said they were lovely and accepted that Donna and Vanner weren't asking them for anything.
The two couples agreed there'd be no custody battle, as they all thought of Vanner as Tim's dad. They just wanted to find out how this had happened, and what to do next.
It turned out the couples had been at the same IVF clinic on the same day, 14 years prior. Donna had gone in for egg retrieval, while Kelly went for embryo implantation for her eldest son, Talon.
DNA tests confirmed Devin was Tim's dad, as well as Talon's meaning the sperm samples hadn't been swapped, but instead Devin's had somehow been used for both.
The two families met in June 2021, with Donna saying it was "surreal" hugging a stranger she'd "made a baby with" - but as Vanner Jr and Tim began to play with Devin and Kelly's kids, Talon, 15, Paxton, 10, and Londyn, eight, her anxiety eased.
Before they left, Vanner asked Tim if he'd like to get a photo with Devin - to which Tim replied he wanted both his dad in the picture. Donna recalled she nearly cried.
The families keep in touch with regular calls, texts and video chats, and have met up several times since. They settled out of court with the clinic in 2022.
