Holy Roman Empire
After the death of Charlemagne, the Holy Roman Emperors got weaker and weaker, until by 924 AD, a hundred years later, nobody even held the title officially. But in 962 AD a German king named Otto got the Pope to name him Holy Roman Emperor anyway, and that started it up again.
Otto's father Henry had been a German lord from Saxony (Northern Germany), elected by the other German lords to lead them. Henry began in a weak position, hardly stronger than the other lords. But he greatly increased his prestige and power by a great victory over Hungarian invasions from the East in 955 AD, and also by attacking Poland. Otto (who is often called Otto the Great) was able to build on his father's work and become even stronger. Otto put his brother and son in positions of power so they could help support him. Otto was also able to use the Church to help him get power. Getting the Pope to name him Holy Roman Emperor was part of this policy. But it also involved taking over Italy again, remembering that Italy and Germany had once been united as the Holy Roman Empire, and trying to recreate that empire. Otto even married an Italian noblewoman, Adelaide.
Otto's son, also named Otto, took over when he died in 973. To show how strong the Holy Roman Emperors were already, this younger Otto married a Byzantine princess, Theophano. When Otto II died young (probably of malaria), he left a three year old son, Otto III, to be king after him.
His mother, the Byzantine princess Theophano, acted as regent the whole time Otto III was growing up (as her aunt Theophano did in Constantinople at the same time). She made a lasting peace treaty with Duke Mieszko of Poland. After Theophano died in 991, Otto III's Grandma Adelaide and powerful Aunt Matilda became the regents. Otto III died in 1002, and the German nobles insisted on electing the next king. But Henry II was still from the same Saxon family. His elected successor, Conrad II, was also related to the Ottos. They, and Conrad's and his son Henry III (1039-1056), all continued the same policies of fighting Poland and trying to take over Italy, while using the Church for their administrators.