[citation needed] Karl August was the third son and child of Albert, 8th Prince of Thurn and Taxis, and his wife, Archduchess Margarethe Klementine of Austria.

[citation needed] After graduating from a local high school, Karl August studied science at the University of Würzburg.

[1] As a committed opponent to Nazism, Karl August forbade his children, after the Machtergreifung, to join the Hitler Youth.

After the death of his elder brother Franz Josef in 1971, Karl August was aged 73 when he succeeded as Head of the House of Thurn and Taxis.

During this time, he was responsible for the modernization of the agricultural and forestry possessions of the House of Thurn and Taxis, and he built homes for his workers and employees.