A married couple who were struggling to conceive were revealed to be Biological Twins after a routine DNA test at a fertility clinic raised suspicion.
The man and woman, who cannot be named for confidentiality reasons, were hoping to try IVF but the lab assistant noticed an abnormal similarity between their DNA profiles.
A doctor at the clinic in Jackson, Mississippi - who also cannot be named - revealed the astonishing events to the local newspaper and explained how the situation had come about.
"It's just a routine thing and we wouldn't normally check to see if there was a relationship between the two samples, but in this case the lab assistant involved was shocked by the similarity of each profile," he told the Mississippi Herald.
His first reaction was that they might be first cousins - until he noted there were far too many similarities in their DNA results.
After realising the man and woman both had the same birthday in 1984, the doctor decided they must be biological twins but didn't know if they were already aware of this or totally oblivious.
When the couple next came for an appointment at the clinic, the doctor says he tried to approach the subject gently. He asked them if they knew they were twins and says they "burst out laughing".
"The husband said that a lot of people remarked on the fact they shared the same birthdays and looked similar to each other, but he said it was just a funny coincidence and that the couple were definitely not related," he said.The doctor says he continued to insist that the pair were twins and had DNA evidence to back it up, after which the wife "pleaded" with him to admit he was joking.
"I wish that I was, but they had to know the truth," he told the Mississippi Herald.
After talking it through with the man and woman, who were trying to process the news, the doctor was able to establish how this had all happened.
The couple had met during college and instantly hit it off, partly down to having such a similar background - the fact they were both adopted after their parents had died.
In truth, their biological parents had died in a car crash when the couple were infants. With no family willing to adopt them, they were put into the care of the state and adopted out into separate families.
But neither of their new families were told that the child had a twin.
What next? According to the doctor, the husband and wife are now considering their future together.
He says he's glad he wasn't able to help them conceive in this case.