Louis I, Grand Duke of Hesse
In 1776, he became engaged to Sophie Dorothea of Württemberg, eldest daughter of Frederick II Eugene, Duke of Württemberg. The engagement was broken off so that Sophia Dorothea could marry Louis's recently widowed brother-in-law Tsarevich Paul Petrovich, son and heir of Catherine II "the Great", Empress of Russia. He received a monetary compensation when the engagement was broken.
Duke Constantine Petrovich of Oldenburg
Tsar Peter III of Russia married on 21 August 1745 to his second cousin, the Prussian princess Sophie Friederike Auguste von Anhalt-Zerbst-Dornburg, better known as Catherine II or Catherine the Great. The couple had one son, Paul, who, after the death of Empress Catherine in 1796, ruled as Emperor Paul I of Russia until his assassination in 1801. Paul and his wife, Maria Feodorovna, Duchess of Württemberg, had 10 children. Their eldest son ruled as Emperor Alexander I of Russia between 1801 and 1825, the period of the Napoleonic Wars.