DNA test reveals man has nine half-siblings linked to his mother’s former fertility doctor 

A routine ancestry DNA test turned into a deeply disturbing family discovery when Joseph Laedtke learned he had nine half-siblings. The unexpected matches appeared to connect him to the Wisconsin fertility doctor who treated his mother decades ago.

Laedtke had taken the DNA test in late 2024 without expecting anything unusual, NBC News reported. Instead, his results showed several people identified as half-siblings. Genealogy tools then appeared to point toward Dr. Frederick Dettmann as their biological connection.

The discovery forced Laedtke’s mother Mary Ellen Lukezich to confront something she never imagined. She had believed her son was conceived using donor sperm after years of fertility treatment. She now alleges that Dettmann may have used his own sperm instead.

Imagine doing a routine ancestry test for fun and finding out your mom’s doctor was a fertility fraudster…

Lukezich and her late husband Thomas Laedtke visited Dettmann in the early 1980s after struggling to have a child. They spent about two years undergoing fertility treatments before agreeing to artificial insemination using donor sperm. 

Lukezich recalled that Dettmann suggested a medical student as the donor. She said the doctor told her the man was unlikely to donate again and was from another state. She also believed the donor had been selected because his appearance closely matched hers and her husband’s.

She kept the fertility treatment private because she considered it a personal family matter, unlike one white couple who just gave birth to a South Asian baby. However, for Lukezich, after becoming pregnant with Joseph, she believed the issue was settled.

That changed when Joseph received his ancestry results. He contacted his mother after seeing multiple potential half-sibling matches. It was only then that he learned his parents had used donor sperm. Surprisingly, the unusual role of donor matching has also surfaced on a hacked dating site recently 

Joseph said genealogy research appeared to connect the matches to Dettmann. He then told his mother what he had discovered. Lukezich was reportedly screaming when she realized what the results could mean.

Joseph said the discovery brought grief for the father who raised him and had died in 2005. As the number of apparent connections became clear, he said he felt “disgust and disappointment.” He described the alleged conduct as a profound betrayal of his mother’s trust.

Lukezich described the experience as deeply violating. She said, “I feel like I’ve been raped.” She also hopes other women who may have experienced similar situations feel able to speak publicly.

Their attorney, Al Foeckler, said several women contacted him after the family shared its story. Some described uncomfortable encounters with Dettmann dating back to the 1970s. Foeckler told NBC News he believes Dettmann was a “serial predator of women.”

Dettmann is now 91 and lives in Arizona. He retired from medical practice during the 1990s.

His attorney, Sean Gaynor, said that Dettmann is aware of the allegations. Gaynor said privacy laws prevent him from discussing patient care. He also said the alleged events date back almost 50 years, and Dettmann has no independent memory of the people involved.

A separate 1985 police report adds another troubling detail. A man told Whitefish Bay police that Dettmann had assaulted his wife during a gynecological examination. Dettmann denied the allegation and prosecutors declined to pursue charges because authorities said the burden of proof was too difficult.

Police records show the complaint was reported to Wisconsin’s medical licensing board. The matter was closed in 1986 after officials considered the facts and voted. The Wisconsin Department of Safety and Professional Services said records from complaints closed that long ago are no longer available.

Gaynor also said Dettmann was never sued or disciplined. He added that his license was never challenged and no ethical complaints were made against him.

The allegations remain disputed. No criminal investigation into Dettmann is currently open with the Whitefish Bay Police Department.