The Kingdom of Württemberg in present-day Germany existed from 1805 to 1918. It was preceded by the Duchy and Electorate of Württemberg and Frederick II, Duke of Württemberg, took the title of King Frederick I on 1 January 1806.
Frederick’s first wife was Duchess Augusta of Brunswick-Wolfenbüttel, and they had three surviving children together before they were separated. Augusta died in 1788 after going into premature labour with a child by her lover. On 18 May 1797, Frederick married Charlotte, Princess Royal and they had one stillborn daughter together. She was thus the first Queen of Württemberg. Frederick died in 1816, and he was succeeded by his eldest son from his first marriage, now King William I.
William’s first marriage to Caroline Augusta of Bavaria had ended in divorce in 1814. They had had no children together. She went on to marry Emperor Francis I of Austria. Shortly before succeeding his father in 1816, he remarried to his first cousin Grand Duchess Catherine Pavlovna of Russia, the widow of Duke George of Oldenburg. They had two daughters together, Maria and Sophie. She would die six months after the birth of Sophie of pneumonia. In 1820, he remarried to another first cousin Duchess Pauline of Württemberg, and they had two daughters and a son together. William reigned for 48 years and was succeeded by his only son, now King Charles I.
Charles had married Grand Duchess Olga Nikolaievna of Russia in 1846, but their marriage remained childless. When he died in 1891, he was succeeded by a male-line descendant of King William I’s brother Paul, who also happened the son of his sister Catherine, now King William II.
William’s first wife was Marie of Waldeck and Pyrmont. They had one surviving daughter, and Marie died before he became King after giving birth to a stillborn daughter. Four years after Marie’s death, he married Charlotte of Schaumburg-Lippe. They would have no children together. In 1918, William was deposed along with several other German monarchs. He and Charlotte were thus the last King and Queen of Württemberg.
With William’s death in 1921, the royal house became extinct, but the headship of the House of Württemberg went to a descendant of King Frederick I’s second youngest brother Alexander, and the line is currently represented by Carl, Duke of Württemberg. Charlotte survived her husband for 25 years.
Complicated story, so many births, deaths, marriages. What is very apparent is that these individuals married within their own class. Some of the close relationship marriages may account for the stillborn births.