A Canadian fertility doctor is facing accusations of using his own sperm to inseminate 11 of his clients, in a class action lawsuit that claims he did so without their knowledge or consent.

The proposed lawsuit against Dr Norman Barwin was first launched in 2016 by an Ottawa family who claimed that the prominent doctor had used his own sperm – rather than that of the family’s father – to conceive their daughter in 1990.

In the months following, the lawyers behind the lawsuit said they had heard from more than 150 individuals with concerns about the doctor’s conduct dating back to the late 1970s.

On Thursday the lawyers said that DNA investigations suggest that 11 individuals whose parents had turned to the doctor for treatment are the biological children of Barwin.

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Those involved are very distressed, lawyer Peter Cronyn told the Ottawa Citizen. “My heart goes out to all of them. Many have demonstrated tremendous courage and are trying their best. It has been very hard.”

The previous statement of claim is currently being amended to include the new allegations, he added. The lawsuit has yet to be certified as a class action.

The lawsuit will also include the concerns of another 51 people whose DNA bore no resemblance to the individuals they had believed to be their fathers. In 16 of these cases, the DNA did not match that of the male parent, while another 35 individuals – all of which had used anonymous donors – were found to have DNA that did not match that of the intended donor. In these cases, the identity of the biological fathers remains unknown.

When contacted by the Guardian, Barwin’s lawyer declined to comment. None of the allegations against Barwin have been tested in court.

The initial statement of claim stemmed from the experience of Davina and Daniel Dixon, who turned to Barwin for help conceiving in 1989. Their daughter Rebecca was born soon after.

More than two decades later a family doctor – responding to questions over how two parents with blue eyes could have conceived a daughter with brown eyes – suggested blood tests. The results suggested that it was impossible that the pair could be father and daughter, according to court documents. DNA testing later backed this finding, suggesting that the probability of paternity was 0.0%.

“I remember just this wave of shock going through my body,” the daughter, Rebecca, told the Canadian Broadcasting Corporation at the time. “It’s not something that you ever would imagine.”

DNA tests later compared her with another woman who – after an ancestry website linked her to one of the doctor’s relatives – said she had been told by Barwin that he was her biological father. The test suggested that the two were “half sisters by way of the same biological father”, according to court documents.

The case has made waves in Ottawa, where Barwin was a high-profile doctor who in 1997 was awarded one of the country’s top honors in recognition of the profound impact his work had had on women’s reproductive health. He stopped practicing in 2014, one year after his license was suspended for two months after he admitted inseminating four women with the wrong sperm.