Charles Lindbergh's secret life came to light after his death

The tests prove that Dyrk and David Hesshaimer and their sister Astrid Bouteuil were the airman's children, said media consultant Anton Schwenk.

All three sprang from a romance between Mr Lindbergh and Munich hat maker Brigitte Hesshaimer that began in 1957.

With a wife and children in the US, the pilot led a double life for decades.

Mystery visitor

Mr Lindbergh, who had six children with his American wife Anne Morrow Lindbergh, became famous as the first man to fly solo across the Atlantic in 1927.

But it was not until 30 years later that his secret affair in Germany began.

Mr Lindbergh fell in love with Brigitte Hesshaimer, more than 20 years his junior, during a trip to Munich in 1957 and continued to see her until his death in 1974.

Mr Lindbergh's German children kept the secret for nearly 30 years

The three children were born between 1958 and 1967 and were listed in official records as "father unknown".

Astrid Bouteuil, now 43, said they remembered Mr Lindbergh as a mystery visitor who would turn up once or twice a year, but it was only after their father died that they learned his identity.

They confronted their mother with a bundle of letters they had found which Mr Lindbergh had written to her.

Ms Bouteuil said her mother had admitted that Mr Lindbergh was their father, but asked them not to disclose the fact while she was still alive.

She died in 2001 at the age of 74.

'Hauntingly familiar'

The Lindbergh family in the US originally regarded the children's claim with scepticism.

However, tests conducted by the University of Munich in October matched the children's DNA with a sample from the airman's grandson, Morgan Lindbergh, who agreed to take part because he thought they looked "hauntingly familiar".

The children say they do not want to make any claim on Mr Lindbergh's estate, but simply wanted acknowledgement that he was really their father.

Now they plan to publish a book about the secret relationship, while a German TV company is making a documentary on the family.

Until the details of his secret life emerged, Mr Lindbergh was seen as a faithful family man.

In 1932, he and his wife were at the focus of world attention when their first child, Charles junior, was kidnapped in New Jersey and found dead 10 weeks later.

The crime, in which a $50,000 ransom was demanded, has never been satisfactorily explained.

Bruno Richard Hauptmann, a German immigrant, was convicted of the child's murder but protested his innocence right up until his execution in 1936.

Mrs Morrow Lindbergh died in 2001, the same year as Ms Hesshaimer, at the age of 94.