Like most twins, 11-month-old Justin and Jordan have a lot in common, but they have different biological fathers.
Admitting she was having an affair with another man at the time the twins were conceived, Mia Washington said she was shocked that it had happened to her:
"I have twins, but they're by different fathers," she told a TV news report.
Washington and fiance James Harrison noticed that the twins had different facial features and decided to have a paternity test. They went to Dallas DNA Lab Clear Diagnostics who said they had never seen a result like this before and that there was a 99.999 per cent chance that Justin and Jordan were fathered by different men.
The highly probable result is that Jordan is Harrison's biological son and Justin's biological father is the man Washington had an affair with.
Doctors say a woman can release more than one egg during ovulation, even without fertility drugs.
Lab Clear Diagnostics' president Genny Thibodeaux described the news as "very crazy", and "most people don't believe it can happen". He said they've never seen this type of result, nor do they expect to see it again.
Doctors call twins that have two different fathers Heteropaternal Superfecundation.
Heteropaternal Superfecundation is so rare, there are only a handful of documented cases in the world.
Medical experts call the boys a miracle of science.
This medical marvel happens when a woman releases multiple eggs during ovulation. If the woman has more than one sexual partner within the same time period, sperm cells can fertilize two separate eggs.
Harrison, the father of one of the twins, said he's forgiven his fiancé's infidelity. He's vowed to stay with her and raise both boys as his own.
He said they are taking it day by day, "it's going to take time to build that trust like we had", he added.
Washington says she regrets the affair, and wants people to know she takes full responsibility for her actions. She wants others to know this can happen, and to be careful before starting an affair.
"Look what happened to me. Think hard about the consequences first, because the most bizarre things can happen when you least expect it!
"James is a good man; he's a great father and genuinely loves both of the twins," said Washington, adding that as far as she was concerned he was the father of both boys because "he's the one there every morning when they get up and every night when they go to sleep".
She plans to tell the boys about their DNA differences when they're old enough to understand.
She has no plans to tell the other father.