Godfrey of Bouillon was one of the most respected Frankish knights. He served the Holy Roman Empire and was one of the leaders of the first crusades.
Even though he was from a noble family he never possessed anything valuable until he inherited the duchy of Lower Lorraine from his uncle. (The duchy is the land bordering Germany and France.)
But Emperor Henry IV didn't let Godfrey have any control of his uncle's land until, he test his loyalty. By 1087 he has proven his loyalty by supporting Henry IV for years though they had many controversies.
The first Crusade started in 1095, when Godfrey heard of this he sold his land and gathered an army of knights to fight in the crusade.
By 1099 his knights were able to scale the city walls of Jerusalem and were some of the first to enter. Later he the leaders of the crusades decided to make Godfrey King. He refuse to have the title king but he still had control of the Jerusalem.
Godfrey had a short rule over Jerusalem, he died in 1100. His brother Baldwin ended up being the new ruler of Jerusalem.