On 4 November1824 in Vienna he married Sophie of Bavaria, a daughter of King Maximilian I of Bavaria by his second wife Karoline of Baden. Franz Karl was an unambitious and generally ineffectual man, although he was a member of the Council that ruled in the stead of his mentally retarded brother Emperor Ferdinand from 1835 to 1848. At the urging of his wife, he renounced his claims to the throne at the time of his brother's abdication in December 1848, allowing their eldest son Franz Joseph to take the throne. Archduke Franz Karl died in Vienna in 1878, six years after the death of his wife.
Issue
Monarchical Styles of Archduke Franz Carl of Austria
married 1) his first cousin Margaretha, Princess of and Duchess in Saxony, (1840-1858) from 1856 to 1858, no issue, married 2) to Maria Annunziata, Princess of the Two-Sicilies (1843-1871) from 1862 to 1871, had issue (three sons and one daughter) and married 3) to Maria Theresia, Infanta of Portugal, (1855-1944), from 1873 to 1899, had issue (two daughters)