DNA test reveals German man was fathered by Nazi donor

A DNA test and documents from Polish wartime archives have overturned the family history of Matthias Kötter, DR reports. The 63-year-old German discovered that he was conceived with sperm from Danish Nazi and Waffen-SS soldier Walther Frisch, while also learning that his biological father had been forcibly sterilised under the Nazi regime.

Kötter, who lives near Frankfurt, took the test in July 2025 as a gift from his children. He had hoped to learn more about his German parents. Instead, the results showed that he was a donor-conceived child with 15 half-siblings, all conceived at Karolinska Hospital in Stockholm.

His half-siblings told him that the donor was Frisch.

“I initially thought it was a scam,” Kötter said.

The discovery shattered his understanding of his childhood. He had been told that it took his mother 10 years to become pregnant, but that it happened naturally. He had never doubted that his father was his biological father.

Clues in a green folder

After learning about the donor, Kötter remembered a green folder he had received from his aunt after his parents died. It contained letters written in old-fashioned German that were difficult to read.

One word caught his attention: “Obrawalde Hospital.”

The family’s official account was that Kötter’s German father, Heinz, had been sent to a labour camp at the age of 17 during the Second World War, contracted tuberculosis and was later admitted to Obrawalde Hospital.

When Kötter investigated the hospital, he found that it had been a psychiatric institution under Nazi control, not a facility for tuberculosis patients.

“It was a place for psychiatric patients. Why did my father end up there?” he asked.

Through a Polish researcher, DR obtained Heinz Kötter’s medical records from the hospital. They showed that he had not been admitted with tuberculosis, but with serious mental health problems diagnosed as schizophrenia.

The Nazis regarded schizophrenia as a hereditary illness, and the diagnosis could effectively amount to a death sentence. About 8,000 patients with hereditary diseases were killed at Obrawalde Hospital.

Heinz, who had trained as a shop assistant, was assigned to register the bodies at the hospital when he was 18. Relatives were given false explanations, such as claims that their family members had died from pneumonia.

Forcibly sterilised

Heinz’s family fought to get him out of the hospital. The letters in the green folder document their efforts.

The Nazis eventually agreed to release him when he was 19, but only after he was forcibly sterilised to prevent him from having children and passing on what they considered a hereditary illness. The procedure was carried out in 1944 at a hospital in the city of Meseritz.

The letters show that Heinz accepted the procedure because he had no choice. He asked his father to keep it secret and not tell anyone what had happened to him.

Kötter now believes that his father could not have had children, which may explain why his parents eventually travelled to Sweden and sought insemination at Karolinska Hospital.

“I do not think my mother knew about the forced sterilisation for many years. But perhaps she was told in the end,” Kötter said.

Demanding answers from Karolinska

Kötter said his mother was inseminated with sperm from Frisch, a member of the regime he had hated throughout his life.

“I am glad that my parents are dead today. The information would have been unbearable for them,” he said.

He is demanding answers from Karolinska Hospital about how the inseminations were possible. Neither the hospital nor Sweden’s national archives has information about Frisch or the many inseminations carried out between 1962 and 1965.

In March, Kötter met three of his half-siblings for the first time at a holiday home near Sjællands Odde in Denmark as part of the documentary series “The mystery of the Danish Nazi donor”. Together, they reviewed the information each of them had found.

As an only child, Kötter said it was overwhelming to suddenly become part of a group of 15 siblings. Some of them are due to meet in Stockholm at the end of August.

“This is something that takes time to process, but one of the positive things is that I have found others who share the same fate, because we have the same biological father,” he said.

“But I will not stop until I have received a better answer from Karolinska than that it has no information. They must search the archives, because this requires an explanation and an apology.”

DR journalist Søren Klovborg is seeking information from anyone who may have knowledge of the case or believe they are a descendant of Walther Frisch. He can be contacted at [email protected].