More than 40 years after his suicide, the shocking secret of pioneering Durban fertility expert Norman "Tony" Walker has emerged - he was himself the father of at least five of the hundreds of children he helped to conceive.
The truth about Walker, who killed himself in 1977 at the age of 62 after the death of his wife from cancer, was revealed after a woman whose mother had used the services of his Durdoc Centre clinic went in search of her biological father.
So far, genetic testing - and late-life confessions by their mothers - have revealed that Walker was the biological father of Cassandra Hallberg and her brother Greg, who live in the US, and of Fiona Darroch, her sister Allison and their brother who live in Australia.
Neither Greg nor Allison wanted their surnames published, and Darroch's brother did not want to be named at all.Now the "diblings" (donor-sperm siblings), who met for the first time in Australia last month to swap stories about their lives, have gone public to trace any other DNA-linked relatives who are unaware of Walker's activities.
The group, who call themselves "Tony's babies", believe there could be many more of Walker's children around the world.
They have established that the doctor - according to a nurse who worked for him - was the main donor at a time when fertility treatment was taboo and sperm donations extremely rare.
They believe that not all those who used Walker's clinic - including couples who were unable to conceive naturally - were aware that the doctor used his own sperm in fertility treatments.
Walker's secret was uncovered thanks to writer Anne Crossey, now living in Ireland, who was conceived through artificial insemination at the clinic.
Crossey told the Sunday Times that after the death of the man she believed to be her biological father, she met an astrologer who told her that her mother was keeping a secret from her.
"I asked my mom and it took her weeks to spit it out," Crossey said.
"My dad wasn't able to have children. Their GP referred them to an obstetrician, Dr Walker, and it turns out that he was running a fertility clinic, an artificial insemination clinic. I was an artificial insemination baby.
"My mom told me that after Walker died, she had contacted his rooms to get her medical records in case she wanted more children so that they could be from the same donor. The secretary told her that Dr Walker had been the main donor."Believing at that stage that she could be one of Walker's babies, Crossey began researching him and found two novels on the internet that he had written under a pseudonym. Under the "review" section she wrote about the fertility clinic and her connection to it.
In Australia, Darroch saw the comments and the penny dropped. She made contact with Crossey.
She had grown up believing Walker was her godfather, and she had a strong relationship with him up until his death.
"My mother had three of us," Darroch said.
"We always wondered if there was something we were not told because we all had blue eyes and our parents' eyes were brown.
"Genetically that did not make sense."
After making contact with Crossey, she confronted her mother, who acknowledged she and her siblings were donor-conceived and that Walker had "mixed the sperm".
She said she subsequently made contact with a nephew of Walker's, Terry Walker, and the genetic link was confirmed through DNA testing. The Sunday Times has seen the results of the testing.
Darroch's daughter, Mary Morrison, who was living in the US, also did a DNA test through the internet site 23andMe, which resulted in Greg and Hallberg learning that they too shared Walker's genes. They made initial contact with Morrison through the site's messaging system.
Greg, who was raised believing he was of German descent, had a test done."My test came back showing that I hadn't had a German ancestor in five generations. This was clearly a surprise," Greg said.
"My dad died in 2000 so I couldn't ask him. And then Fiona's daughter suddenly showed up on the site as being my niece.
"I got in touch with Fiona and she explained it all. I knew she was right because Dr Walker was a family friend . I remember how upset my mom was when she found he had died."
Greg also confronted his mother, who admitted he and his sister had been donor-conceived at Walker's clinic and that Walker was the donor.
But the children Walker had with his wife want nothing to do with the "babies" group.
A family representative told the Sunday Times no genetic testing had been done on any of Walker's acknowledged children or grandchildren linking them to the "diblings".
"Thus there is no proof that he was the donor. The only potential genetic proof to date is that the 'diblings' are genetically linked. All other statements are not based on genetic proof.
"South African law states that sperm donors are anonymous. Please refrain from mentioning Dr Walker's name until consent and genetic proof is obtained from his family."Crossey's own DNA results showed Walker was not her biological father. The other five "babies" were born in the 1960s but she was born in May 1975, and believes that by then Walker had increased his pool of donors. She still hopes to find out who her father is and if she has any true "diblings".
"Whatever happens, whether I find DNA siblings or not, it's a magical story," Crossey said.
"There's something very profound about what Dr Walker was doing. He was making life happen, and we're all very grateful for that. I have the utmost respect for him as a man and a pioneer. But I wish he had kept proper records."
Darroch said: "I am guessing there are lots of us out there, most of whom would be totally unaware of their [true] paternity. This story . may help my yet undiscovered siblings to find some answers if they are searching for explanations about their identity and paternity."
At the time Walker ran the Durdoc Centre clinic there was no legislation governing sperm donation and artificial conception.
In SA today, legislation regulating assisted reproduction contained in the Children's Act still precludes a donor-conceived child from ever knowing the identity of the donor...