A father and son pleaded guilty in a German court Tuesday over a plot to blackmail the family of Michael Schumacher by threatening to release images of the Formula One legend.

The men from Wuppertal in western Germany made the admission at the opening of their trial in the city, a court spokeswoman said. 

The men, identified only as Yilmaz T. and Daniel L. , allegedly threatened to release private photos and videos of Schumacher and demanded 15 million euros ($15.7 million) from his family.

These purportedly included images of the seven-time Formula One champion before and after a 2013 skiing accident, which left him with a serious brain injury.

Schumacher, 55, has not been seen in public since.

A third man, who is accused of supplying the photos to the other two defendants, also went on trial for his alleged part in the plot but made no admission of guilt.

The man, identified as Markus F. from the western German town of Wuelfrath, worked as a security guard at the Schumacher family residence in Switzerland until 2021.

Prosecutors accuse the suspect of selling images of Schumacher, acquired during his work, to the father and son for a "five-figure" sum.

According to prosecutors, Yilmaz T. rang an employee of the Schumacher family several times in June this year to demand money.

The employee demanded proof of the images, which were delivered from a new email address, said to have been set up by the suspected blackmailer's son.

The court has scheduled a total of five hearings until mid-February.