On this day in history in 1933, Princess Thyra of Denmark died in Gmunden, Upper Austria. Thyra was the sister of Frederik VIII of Denmark, Queen Alexandra of the United Kingdom, George I of Greece and Empress Maria Feodorovna of Russia (Dagmar of Denmark). In December 1878, she married Crown Prince Ernest Augustus of Hanover, 3rd Duke of Cumberland and Teviotdale.
When reading about Princess Thyra I found out she had an illegitimate daughter. The father was Vilhelm Frimann Marcher, a lieutenant in the cavalry. She had the baby in Athens, Greece, where her brother ruled as George I. The press was told she had jaundice. She gave birth to a daughter named Maria on 8 November 1871. Apparently, the child was adopted by a Rasmus and Anne Marie Jørgensen and Maria was renamed Kate. In 1902 Kate married Frode Pløyen-Holstein. They were apparently childless and she died in 1964. Vilhelm Frimann Marcher killed himself on 4 January 1872 after a confrontation with the Danish king.
It doesn’t appear to have been a huge scandal at the time. The secret was probably well kept. Princess Thyra married quite well for a ‘tainted’ princess.
Vilhelm Frimann Marcher
Possibly Kate/Maria with her adoptive mother
Kate/Maria in 1896
This story is also discussed in A Royal Family, a documentary about the house of Glücksburg. The documentary is in Danish, but the interviews are in English.