They fell in love - then had to check they weren't brother and sister

Audrey and Arthur Kermalvezen met at a gathering of donor-conceived activists

A close-up photograph shows a man and a woman - both with brown hair - posing together outdoors and looking toward the camera. The man wears a white hat. The backdrop is a city street with a building façade, outdoor seating and an orange scooter visible in the background.

For years, Arthur Kermalvezen, the child of a sperm donor, saw possible fathers everywhere he went. "I imagined it might be my teacher, the people I saw on the bus... and I was very angry because it's impossible to live like this."

When, as an adult, he fell in love with Audrey, another sperm donor baby from Paris, the question became even more pressing.

Audrey describes the moment they met at a gathering for donor conceived activists in 2010 as "love at first sight" - but was this connection a romantic or genetic attraction?

When they were born, there were only two sperm banks in Paris and many men had made multiple donations - so there was a real possibility they could be half-siblings.

Before building a life together, Arthur and Audrey needed to know whether they were related. But in France, laws governing genetic testing and donor anonymity made finding the answer extremely difficult.

In France, only a research scientist, doctor or judge can order and supervise a genetic test, and people can be fined more than €3,500 ($4,288; £3,191) for possessing a home testing kit. As a result, companies such as 23andMe, Ancestry and MyHeritage don't make their kits available in France.

Supporters of the law, in place since 1994, say it stops sensitive genetic data being given to commercial companies, and prevents family disputes being caused by unexpected results.

But Arthur points out that France is the only country in Europe that criminalises the use of such tests.

Even before her parents told her as an adult that she was donor-conceived, Audrey had qualified as a lawyer, specialising in bioethics law. Because of this, she fully understood that French law had guaranteed donor anonymity, even after a donor's death.

But Audrey had been conceived in 1979, before any such legislation existed.

Audrey and Arthur have both campaigned for the right to know one's origins

While searching for other donor-conceived people born before 1994, Audrey came across Arthur. He had written a book detailing his desire to learn more about his biological origins.

Audrey says she was struck by how precisely he expressed feelings she herself had struggled to articulate. Both had loving families, yet both found themselves drawn to questions about the unknown people who had helped to create them.

When they met in person the chemistry was immediate. So was the problem.

Before they could move from platonic friendship to a romantic relationship, and even build a life together, they had to know the truth about their fathers. But no one in authority was willing to tell them.

After months of searching, they found a doctor in southern France who, for €900 ($1,028; £764) in cash, conducted a genetic test which found that they were not related. But their unease remained as the doctor was breaking the law in sharing that result with them.