A woman from Sacramento, California, began tracking down her Irish father when a biology lesson in high school made her realize she was not genetically related to her parents.

Courtney Hardy, now 27, tracked down her father Emmanuel Cullen, a Belfast man.

The Fox 40 news account executive shared her story on Facebook Stories.

Hardy told the Belfast Telegraph about the illuminating high-school biology class. She said, “We were learning about dominant and recessive traits. My teacher was using eye colour as an example of how two blue-eyed parents have almost a 0% chance of having a brown-eyed child.

"That was my situation, both of my parents had blue eyes and mine are brown. I went home from school that day and talked to them about it and my parents told me I was actually adopted."

At the time Hardy was 15-years-old. She waited another seven years before she started to trace her birth parents.

At 22 she wrote to the State of California, asking for more information about her birth. She received a packet of the information they had on file including some details, the ages of her brothers and details of her birth in San Diego.

Then, she explained in her Facebook story, “I had a list of known family members that I plugged into Facebook. Almost instantly, I had found a cousin by marriage who lived in Hawaii. She was only 18 years-old, and I wrote to her explaining that I was searching for my birth family. I got a response in less than an hour. I had no idea if I was really ready for this.”

She found her mother, Wendy Moten, from San Diego and connected with her the very next day.

Moten introduced Hardy to her new family and told her that her father was Belfast-born Emmanuel Cullen.

When Cullen heard the news he said that he was “blown away”.

He said, “Her mother got in touch with me and said 'Are you sitting down, because I have a bombshell for you'.

"I thought something was wrong with my son - who is my daughter's full brother - but she said "you also have a daughter. I was going through all kinds of emotions. I was ecstatic, as I've always wanted a daughter.”

Cullen described that first time he met his daughter. He said, “It was so emotional, as soon as I saw her it was instant.

“We just hugged each other and she was welcomed with open arms. She's a diamond. She did it all herself."

Hardy, an account executive at FOX 40 news, had lived with her adoptive parents Ken and Nancy. In August 2011 she met with her father and two step-brothers, Ryan and Tony, in Belfast.

She said, "I remember walking up to them and they couldn't believe how much I resembled. When I left, my family told me if home ever didn't feel right, I always had a home in Belfast.”

But Hardy insisted Ken and Nancy, her adoptive parents, will not be replaced.

Hardy said, “To have found my birth parents, it's great. But my parents will always be my parents, no matter what. I was very lucky to grow up with two very loving, caring and dedicated parents. They were at every basketball game, soccer game, school play, graduation. I was just always curious about who my biological family was and what it would be like to have siblings since I grew up an only child.’’

Cullen shared his praise for how Hardy turned out. She said, “She had a very good upbringing, her parents are just great people. I thanked them for the brilliant job they had done. I couldn't ask for anything better.

"I just can't wait until she comes back again.”

On Facebook she finished her tale by saying, “These journeys have taken me to San Diego, Seattle, Phoenix, Ireland and England, and have opened up my world in a way I didn't know was possible. Meeting my relatives has given me perspective on how profoundly lucky I am to have such wonderful and supportive parents, as well as an extended birth family in my life. In a way, through getting to know them, I feel like I've finally gotten to know myself.”