Short answers, pulled from the story.
The House of Habsburg, also known as the House of Austria, was one of the most powerful dynasties in Western history. It ruled vast realms across Europe and the Americas during the Middle Ages and early modern period, including the Holy Roman Empire and Spain.
The House of Habsburg took its name from Habsburg Castle, a fortress built in the 1020s in present-day Switzerland by Radbot of Klettgau. The name may derive from the High German Habichtsburg, meaning hawk castle, or from the Middle High German hab, meaning a ford. The first documented use of the name by the family dates to 1108.
Count Rudolph I was elected King of the Romans on the 1st of October 1273, then defeated and killed King Ottokar II of Bohemia at the Battle of Marchfeld in 1278. He appointed his sons as Dukes of Austria and moved the family's power base to Vienna, where the dynasty became known as the House of Austria and ruled until 1918.
The House of Habsburg split after the abdication of Emperor Charles V in 1556. The Austrian, or German, branch was led by his brother Ferdinand, who became Holy Roman Emperor, while the Spanish branch was led by his son Philip, who became Philip II of Spain.
The Habsburg jaw is mandibular prognathism, an enlarged lower jaw with an extended chin seen in many family members. A 2019 study found that the degree of mandibular prognathism showed a statistically significant correlation with the degree of inbreeding caused by frequent consanguineous marriages.
Habsburg rule in Spain ended after the death of Charles II in 1700 and the War of the Spanish Succession, won by the House of Bourbon. The main dynasty ruled in Vienna until the 11th of November 1918, when Charles I of Austria renounced any role in state affairs following defeat in World War I.