Fiona Darroch grew up close to her godfather Dr Tony Walker.
Her parents had tried for more than five years to have a baby, before visiting fertility expert Dr Walker - known for his 'miracle babies' - who helped them conceive not just Fiona, but her younger brother and sister as well.
The family became close to Dr Walker and his wife Molly until their deaths, just a month apart, when Fiona was 16.
Fiona Darroch told her story on SBS Insight. Post continues below video.
For decades, Fiona held onto the photographs, letters and war medals of her godfather. She even had his first-ever driver's license, which he'd gifted her because she liked the photo.
In 2014, clinical psychologist Fiona was at work when a number of colleagues began to joke about how some children look nothing like their fathers, before the conversation turned to genetics and eye colour.
She - blonde and blue-eyed - had a niggling thought. How likely would it be for two dark-eyed parents to have a blue-eyed baby? How likely to have a green-eyed baby, like her younger sister?
She Googled the possibilities, all the while imagining Dr Walker's blue eyes.