Emperor
The first Austrian Emperor was the last Holy Roman Emperor Francis II. In the face of aggressions by Napoleon, Francis feared for the future of the Holy Roman Empire. He wished to maintain his and his family's Imperial status in the event that the Holy Roman Empire should be dissolved, as it indeed was in 1806 when an Austrian-led army suffered a humiliating defeat at the Battle of Austerlitz. After which, the victorious Napoleon proceeded to dismantle the old "Reich" by severing a good portion from the empire and turning it into a separate Confederation of the Rhine. With the size of his imperial realm significantly reduced, Francis II, "Holy Roman Emperor" became Francis I, "Emperor of Austria". The new imperial title may have sounded less prestigious than the old one, but Francis' dynasty continued to rule from Austria and a Habsburg monarch was still an emperor ("Kaiser"), and not just merely a king ("König"), in name.
List of rulers of Württemberg
The Holy Roman Empire came to an end in 1806. The Elector of Württemberg, allied to Napoleon I, anticipated its dissolution by becoming the ruler of an independent Kingdom of Württemberg in 1806.
Because of a lack of male heirs under Salic law, on the death of Wilhelm II in 1921 the royal house had to reach back to the descendants of Friedrich II Eugen (ruled 1795–97). The line of the Duke of Urach was excluded because of a morganatic marriage back in 1800 by its forebear Duke William, and so the succession devolved to the younger branch of Altshausen.