Background
He was born in Vienna, the third son of Emperor Francis II (I) by his second marriage with Princess Maria Theresa from the House of Bourbon, daughter of King Ferdinand I of the Two Sicilies and Maria Carolina of Habsburg-Lorraine. On 4 November 1824 in Vienna he married Princess Sophie of Bavaria from the House of Wittelsbach, a daughter of King Maximilian I Joseph of Bavaria by his second wife Caroline of Baden (Sophie"s paternal half-sister, Caroline Augusta of Bavaria was by this time Franz Karl"s stepmother, having married his thrice-widowed father in 1816) The Wittelsbach condoned the unappealing manners of her husband in consideration of the incapability of his elder brother Ferdinand and Sophie"s chance to become Austrian Empress.