Initially remaining a Lutheran until 1818, by marriage he established the Catholic branch of the family, which eventually gained the thrones of Portugal (1837) and Bulgaria (1887).

Ferdinand's nephews and nieces included Queen Victoria of the United Kingdom and her husband Prince Albert, as well as Empress Carlota of Mexico and her brother King Leopold II of Belgium.

On 1 February 1802 he transferred to the Austrian Army serving in the Chevauxleger-Regiment Fürst Rosenberg in which he was promoted to major on 29 September 1804.

In Vienna on 30 November 1815, Ferdinand married Princess Maria Antonia Koháry de Csábrág et Szitnya, daughter and sole heiress of Ferenc József, Prince Koháry de Csábrág et Szitnya, converting to Roman Catholicism in 1818.

[2] When Antonia's father died in 1826, she inherited his estates in Hungary, and Ferdinand took the title of Duke of Saxe-Coburg and Gotha-Koháry.