Two strangers who were born just months apart and live in the same American city have united after discovering 35 years later they have the same Kiwi father.
And the New Zealand man, a doctor, is believed to have secretly fathered at least three other children.
Phoenix woman Amy Measeles was told 14 years ago by her mother she was conceived using a sperm donor.
Shocked by the news, Measeles decided to take a DNA test to find who her real father was - but her journey uncovered another secret: she had a sister.
Across town in Phoenix, Emily Sinclair spent the first 35 years of her life thinking she knew who her father was.
She never knew she was conceived by a sperm donor, but it wasn't until Measeles tracked her down that Sinclair learned she had a sister and the same father via sperm donation.
Sinclair and Measeles were both conceived by the same Kiwi doctor who lived in the US more than 30 years ago.
The two women were conceived using sperm from the same New Zealand doctor who lived in the US over 30 years ago, and managed to anonymously father at least five children in Phoenix, Arizona during his short time here.
"We're all basically 35 from Phoenix," Sinclair told Fox 10 Phoenix.
"We sat down, we want somebody that looked they would fit with us, and that's pretty much - that's all," Measeles told the TV channel.
"There were no records kept. They didn't imagine people would figure out, so everything was secretive. When Mum told me, it made sense because I always knew, growing up, no way you took my mum and my dad and created me. There's always something off."
Measeles said her mother explained her dad struggled with fertility and the couple sought help from a doctor.
Meanwhile, unaware of her family history Sinclair decided to take a DNA test home with her husband to learn about their family origins.
But she soon noticed a number of unfamiliar names in her "top matches" list. Not long after her test, Measeles got in touch in Sinclair.
Following the startling news, Sinclair confronted her mother asking for the truth where she confessed - the Kiwi doctor was Sinclair's biological father."So, they really wanted a kid, and were told mix a donor sperm and your husband's sperm, and maybe it will activate his, and you never know, just don't tell anybody, and that's what they did," said Sinclair.
The news devastated Sinclair, telling Fox 10 Phoenix she was upset her Dad acted like nothing had happened and revealed she needed to take two months off work to process the heavy news.
After doing some research Sinclair then found an email address for her biological Kiwi father and sent him a message.
He soon replied and explained there was no medical history to worry about.
The half-sisters' biological father revealed he was a Phoenix resident between 1979 and 1983 but said their parents didn't want a relationship with him because "that wasn't the purpose".
However, he also revealed he had two sons but didn't tell anyone about them.
Now Measeles and Sinclair are close friends with the sisters often mistaken for twins from time to time.
"I went from having one brother, and now I have three brothers and three sisters," Measeles said.
The New Zealand doctor has not been named in media reports.