(CNN) A doctor who ran a fertility clinic in Canada used his own sperm to father at least 11 children, a class-action lawsuit alleges.

Dr. Norman Barwin is accused of using his sperm without the knowledge or consent of the families who approached him for insemination treatment at his clinic, according to the suit.

"We are now aware of 11 individuals whose parents went to Dr. Barwin for assistance with fertility, and DNA investigation discloses that he is their biological father," says a statement from Ottawa law firm Nelligan O'Brien Payne, which filed the suit.

The suit alleges that in some cases, Barwin was supposed to use the sperm from the male of the couple for insemination; in other cases, he was expected to use an anonymous sperm donor. "Instead, it turns out that Dr. Barwin himself is the biological father," the statement says.

Attorneys representing Barwin declined to comment to CNN.

Peter Cronyn, one of the lawyers representing the plaintiffs, accused the doctor of a tremendous breach of trust. He said his firm expected to find that the doctor was the father of some children, but it didn't "think it was going to be quite as much as we found."

"When people have discovered that their children are not as what was intended, it's a very distressing discovery," Cronyn told the CBC , an affiliate of CNN.

The law firm says the allegations date as far as the 1970s, when Barwin ran the Broadview Fertility Clinic and practiced out of a fertility clinic at Ottawa General Hospital. The most recent case is from the early 2000s, the suit claims.

In addition, at least another 16 children were found not to be biological matches to the men previously believed to be their fathers, according to the statement from the plaintiffs' law firm. In those cases, the actual sperm donor is unknown, the statement says.

A further 35 children may not have been conceived using the anonymous donor sperm chosen by their mothers. Their fathers' identities were also unknown, the statement says.

Barwin was suspended by the College of Physicians and Surgeons of Ontario for two months in 2013 after he admitted that he inseminated four women with the wrong sperm over two decades.

Rebecca Dixon was one of the original plaintiffs in the lawsuit, which began in 2016.

Dixon, whose parents had gone to Barwin's clinic in 1989 to help conceive, learned that her DNA did not match that of the man she believed was her father, the lawsuit says. When Dixon and her family learned this news, they began researching Barwin's clinic. "They could not help but notice that Rebecca bore an uncanny physical resemblance to Dr. Barwin," the suit says.

Dixon eventually connected over the Internet with Kat Palmer, who had also been conceived at Barwin's clinic, according to the suit. Palmer had done research after undergoing a DNA test via an ancestry website. From those results, she believed she was related to Barwin.

On October 27, 2015, the suit says, she got her answer via email from the doctor: "Barwin confirmed that he was her biological father."

Dixon and Palmer compared their DNA results and found that their fathers were a match, the suit alleges.

Dixon told the CBC that she had initially been hesitant to move forward with the suit but was now glad she did.

"As I've realized the extent of what Barwin has done and the number of people he has affected in so many different ways," she said, "it certainly made me feel even more strongly that we're doing the right thing."

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A lawsuit filed this month in the United States accuses a doctor at a fertility clinic of using his own sperm to inseminate a woman in 1980; the family says the woman's daughter learned of it through an Ancestry.com DNA test.

A 1993 wire article in The New York Times reported that a fertility doctor inseminated patients with his own sperm and led others to believe that they were pregnant when they were not. He was sentenced to five years in prison and ordered to pay $116,805 in fines and restitution.