When Donna and Vanner Johnson purchased an at-home DNA testing kit, they were hoping to learn a little more about themselves and have some fun with it.
But when they got their results back, everything they thought they knew about themselves turned out to be false.
The pair soon learned that their 12-year-old son wasn't biologically Vanner's child.
The boy had been conceived through IVF treatment at a clinic and it appears there was a mix-up and Donna's egg was fertilised with a stranger's sperm.
Speaking to ABC4.com, the couple from Utah, in the US, explained how their lives had been turned upside down.
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Vanner recalled: "When I looked on that page and saw mum for him and father unknown, I thought 'what do you mean father unknown?'
"I am his father."
He continued to say: "There were a lot of emotions we had to work through including separating the love of our son which has not changed.
"This mistake that happened, how could it happen, why did it happen and what do we do now."
The clinic where the couple received their fertility treatment has since confirmed that a stranger's sperm was used to fertilise Donna's egg.
The parents decided not to tell their son the news right away as they processed what had happened.
After a year had passed, Donna and Vanner decided to try and track down their son's biological father who had attended the clinic on the same day as them.
The families then had an awkward phone conversation and have since travelled from their home to meet the man.
Both of the couples are currently in the process of taking legal action against the fertility clinic.
Vanner added: "It’s grossly inadequate what we are dealing with.
"And as we got going through that process… I thought because of what we are dealing with, it would be treated differently or more gingerly and it’s not at all."
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