Dan and Davina Dixon wanted desperately to have a baby, but for years they couldn't conceive on their own. So in the late 1980s, they sought out Norman Barwin, one of Canada's leading fertility specialists.

He was "incredibly well regarded" - a doctor who was as much an activist as a scientist, the couple's attorney told The Washington Post.

Barwin had been the president of the Canadian Fertility Society and Planned Parenthood, and he founded an abortion-rights organization, Canadians for Choice. He would eventually be inducted into the Order of Canada, the nation's second-highest civilian honor.

Patients who anguished over not being able to conceive revered Barwin as a "baby god."

In court documents, the Dixons recalled a warm bedside manner that put them at ease during what could be a stressful and sterile medical procedure at the Broadview Fertility Clinic in Ottawa.

Alone in the room with the couple in 1989, the doctor held up a straw full of sperm, according to their attorney, Frances Munn. The straw had Dan Dixon's name written on it - proof that no matter the circumstances of conception, the baby would be theirs.

Soon Davina Dixon was pregnant. And on June 1, 1990, she gave birth to a healthy, brown-eyed girl. They named her Rebecca.

Twenty-six years later, the family learned the crushing truth: Dan Dixon wasn't Rebecca's biological father. Barwin was. They discovered the shocking news only after stumbling upon a Facebook post that raised a nagging question, according to court documents.

"They were trusting [Barwin] with the creation of life," Munn said. "They were trusting him with Daniel's sperm. He trusted him to carry on his bloodline.

"I can't think of a higher level of trust that you would put in someone - or a higher betrayal."

The stunning revelation seven months ago led to another: Rebecca Dixon learned that she has a half-sister - another child of Barwin's, who was also conceived at the doctor's clinic with the doctor's sperm. That woman's parents, a Vancouver couple, thought the sperm was from an anonymous donor.

The Dixons' claims, filed Monday in Ontario Superior Court, are a precursor to a potential class-action lawsuit against Barwin. The family hopes that spreading the word about their ordeal will help them find other people who have been fathered by Barwin - Rebecca Dixon's biological half-siblings.

In an email, Barwin's attorney told The Washington Post that "a statement of defence on behalf of Dr. Barwin will be filed with the court in due course. At this time, Dr. Barwin and I have no direct comments to make to you in this confidential matter."

Munn said she didn't know how many plaintiffs could ultimately be involved in the forthcoming lawsuit. After they have completed a search for potential victims, lawyers would have to decide whether it's best to file individual lawsuits or to seek class-action status.

"We're hoping that people come to us," she told The Post. "We'll have to go through everyone's claim one by one. For our purposes, we want to figure out who's out there, and then we'll have to sort out the rest."

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Brown-eyed baby

The family's suspicions were aroused in February when Davina Dixon saw something on Facebook that piqued her interest, according to the legal claim. The post, according to the court filing, said that "it was unusual for two individuals with blue eyes to give birth to a child with brown eyes. (Davina) was concerned because she and Daniel have blue eyes and Rebecca has brown eyes."

Rebecca Dixon also worried that she was gluten-sensitive and had celiac disease, Munn said. The disease runs in families, but none of the Dixons had it. She booked an appointment with the family doctor, hoping he would allay her family's worries and "reassure her that the Facebook post was a myth."

He didn't. Instead, the doctor suggested that Rebecca Dixon's blood type be tested against her father's, the court filing says.

Daniel Dixon has type AB blood; his daughter is O-positive. That's medically impossible for a biological father and daughter, the doctor told the family.

An April DNA test confirmed their fears, the court filing says: "Daniel could not be the biological father of Rebecca. The probability of his paternity was 0.0 percent."

Even before the discovery, Barwin was facing legal problems.

Five women involved in four fertility procedures over a decade had received the wrong sperm at the Broadview Fertility Clinic, according to the Canadian Broadcasting Corp. Two of the women filed $1 million lawsuits against the clinic, in 2004 and 2006. Both suits were settled out of court, so the details weren't publicly available.

But the accusations in the lawsuits became public in a medical disciplinary hearing in 2013. The College of Physicians and Surgeons of Ontario found Barwin guilty of professional misconduct for mixing up sperm samples. He received a reprimand and was banned from practicing medicine for two months.

"I regret that I've caused these patients any difficulties," Barwin said in a statement at the hearing, according to the Toronto Star. "My interest was always to do the best for them."

The chairman of the College of Physicians and Surgeons panel that heard the case excoriated Barwin for what he called a series of "tragic outcomes."

"It is hard to imagine a more fundamental error in your former specialty than failure to impregnate the right woman with the right sperm," William King said, according to the Star.

King, the newspaper reported, noted that Barwin had "contributed over the years to the care of many difficult patients." But, King said: "The negative effects arising from these cases would be hard to exaggerate. Your errors have condemned them to social and psychological pain and their offspring to ignorance of their genetic heritage."

Barwin had already retired from fertility work at that point, volunteering to stop artificially inseminating women in 2012. A year later, he became one of a handful of Canadians to have the Order of Canada honor revoked.

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Rebecca's search

After the DNA test, Rebecca Dixon was desperate to learn more about her ancestry. So she turned to the Internet. She submitted her DNA to the website 23andme and learned that her ancestry was almost 60 percent Ashkenazi Jewish.

Barwin is "a well-known member of the Jewish community in Ottawa," according to the court filing.

The Dixons then learned about the lawsuits against Barwin from a decade earlier. They also "could not help but notice that Rebecca bore an uncanny physical resemblance to Dr. Barwin," the legal claim says.

In September, Rebecca Dixon connected with a woman named Kathryn Palmer, who lives in Vancouver and was also conceived at Barwin's clinic in Ottawa. Palmer's parents wanted to conceive via an anonymous sperm donor; their daughter was born Jan. 31, 1991.

Palmer was curious about her genetic background and wanted to locate her sperm donor, so she submitted her DNA to the ancestry website Family Tree DNA. She was matched with a man the site said was a second cousin. He lived in New York City, and he was a relative of Barwin's.

Palmer ultimately contacted Barwin, who agreed to perform a DNA test and confirmed that Palmer was his biological daughter, the court filing says.

Using DNA tests, Palmer and Dixon found that they were half-sisters with the same father. It was then that Rebecca Dixon knew: Her biological father wasn't Dan Dixon. It was Norman Barwin.

Now, the Palmers and Dixons are waiting on a response from Barwin and his attorneys to the legal filing.

The Dixons join a small fraternity of families outraged over wrongdoing by fertility doctors.

Recently, a retired doctor in Indiana told six people who suspected they were his children that he had used his own sperm in about 50 insemination procedures starting in the 1970s. According to CBS News, Ronald Cline had told his patients that they were receiving sperm from medical students.

Cline pleaded not guilty on Monday to two charges of obstruction of justice.

Another fertility specialist, Cecil Jacobson, may have fathered as many as 70 children from 1976 to 1998 in Northern Virginia, CBS reported.

Munn said the Dixons have no idea how many children were conceived with Barwin's sperm at his clinic, which he operated for three decades. They hope to compel him to provide a sample that might allow other victims to undergo DNA tests.

When the family first found out about the deception, Rebecca Dixon "was in tears," her father told the CBC. "I was in tears because that meant for sure she was not my child. We had no idea whose child she was, but she was not my child. And I just went to bed and cried."

Of Barwin, he said: "I could give him a big kiss or slap him across the head. I'm happy that we have Rebecca, and yet, I'm angry with what he did."

Davina Dixon told the CBC that she "was furious; I felt violated." Barwin, she said, "fathered these children. And he just had no right to do that."

Rebecca Dixon told the CBC that she is now at peace with the revelations. "It doesn't diminish anything I knew about myself, any of the relationships I have, the love between my parents and I, and the memories I have growing up," she said. "It just adds a new thread to the story - a complicated thread that's difficult in some ways, and with some positives. It's another part of my story."