Image copyright Courtesy Rebecca Dixon Image caption The Dixon family learned this year Daniel was not Rebecca's biological father.

A former Ontario fertility doctor is facing allegations he used his own sperm to impregnate at least two patients.

Daniel and Davina Dixon and their daughter Rebecca filed a civil lawsuit this week in an Ontario court against Dr Norman Barwin.

They decided to take legal action after learning this year Rebecca was not Mr Dixon's biological daughter.

They are seeking punitive and other damages against the doctor.

The Dixons contacted Dr Barwin in 1989 to help them get pregnant.

According to the statement of claim filed on Tuesday in the Ontario Superior Court of Justice, Dr Barwin collected a sample of Mr Dixon's sperm, which the couple believed was used in the successful treatments.

Rebecca, now 26, was born in 1990.

"From the time of Rebecca's birth and into her childhood, teenage, and young adult years, Rebecca, Daniel, and Davina believed that Rebecca was Daniel's biological daughter," the document says.

Image copyright CBC Image caption A lawsuit alleges Dr Norman Barwin used his sperm to impregnate at least two of his fertility clinic patients

They began to suspect a possible mix up when Ms Dixon saw a Facebook post in February about how it was unusual for two individuals with blue eyes to give birth to a child with brown eyes.

"She was concerned because she and Daniel have blue eyes and Rebecca has brown eyes," says the statement of claim.

'Uncanny resemblance'

The family had both a blood test and a DNA test performed. They confirmed there was no chance Mr Dixon was Rebecca's father.

They began to dig into Dr Barwin's history. He was sanctioned in 2013 for artificially inseminating three patients with the wrong sperm at his Ottawa clinic.

They also noticed "Rebecca bore an uncanny physical resemblance to Dr. Barwin".

A few months later, Rebecca Dixon connected online with Kathryn Palmer, 25, who had discovered in 2015 that Dr Barwin was her biological father. Ms Palmer's parents were also Dr Barwin's patients.

Both women underwent a second DNA test. The results indicated they were half-sisters.

The Dixon family lawyer alleges it is possible Dr Barwin used his own sperm to impregnate other patients and that she will seek to certify the claim as a class action lawsuit if more people come forward.

None of the allegations against Dr Barwin have been proven in court and his lawyer said a statement of defence will be filed in the coming weeks.