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.
Archduke Simeon of Austria
Simeon married Princess María of Bourbon-Two Sicilies, second-eldest daughter of Infante Carlos, Duke of Calabria and his wife Princess Anne of Orléans, on 13 July 1996 in La Toledana, Spain. Simeon is a (half) second cousin of his wife's father, both being great-grandchildren of Robert I, Duke of Parma. María's father descends from Duke Robert's first marriage and Simeon from the Duke's second marriage.