It had to depend on the higher authorities in Gotha for the matters of administration of its three districts, Saalfeld, Grafenthal and Probstzella – the so-called "Nexus Gothanus" – because that was the residence of John Ernest's oldest brother, who ruled as Frederick I, Duke of Saxe-Gotha-Altenburg.

In 1747 Francis Josias was able to anchor his birthright (primogeniture) in the Line of Succession laws and confer it on his rapidly growing family for the long-term survival of the House of Saxe-Coburg-Saalfeld.

His brother and Regent Duke Ernest Frederick was known more for the perilous finances of his Duchy, which underwent from 1773 onwards a forced management of debts by an Imperial Debit Commission until 1802 and affected the fortunes of his successors.

Another daughter, Princess Marie Luise Victoire, married Prince Edward, Duke of Kent and Strathearn, in 1818, and became the mother of Queen Victoria.

In 1816, his elder brother, Prince Ferdinand, married Maria Antonia Koháry de Csábrág, who came from one of the wealthiest aristocratic families in Hungary, and founded the Catholic line of Saxe-Coburg-Koháry.

The towns of Fürth am Berg, Hof an der Steinach, Niederfüllbach and Triebsdorf came to Saxe-Coburg; Gleußen, the Schleifenhan mill, Buch am Forst and Herreth went to Bavaria.

In 1815, as the reward for fighting in 1813 on the Allied side against Napoleon, the Congress of Vienna sent an area left of the Rhine River, later called the Principality of Lichtenberg, a territorial gain as well as membership in the German Confederation for the sovereign.

On 12 November 1826 the decision, from the arbitration of the supreme head of the family, King Frederick Augustus I of Saxony, resulted in the extensive rearrangement of the Ernestine duchies.