Kristallinchen post on the Scandalous Royals thread makes me remember about Princesse Louise of Belgium and Prince Philipp of Saxe-Coburg and Gotha.
They were married on 1875 when Louise was seventeen and Philipp thirty-one.
Louise ran away from their bedroom on her wedding night and went crying to her mother about the "awful things" her husband had just done to her. A very bad start for a marriage
The couple managed to have two children and after twenty years Louise fell in love with Count Geza Mattachich. She left Vienna in 1897 to follow him, taking her daughter Dorothea with her. Enormous scandal ensued. Philipp and Geza even fought a duel in 1898.
Geza was later imprisoned for four years.
Louise began divorce procedings but there were not finalized until 1906. She and Geza then went to live together in Paris until their respective deaths in 1924 and 1923.