In actuality, these demons are fallen angels that rebelled alongside Lucifer who was once an archangel that defied God and created a war in Heaven. After their fall from grace, each of the beings were twisted and transformed into hideous abominations. Their counterparts are the Seven Archangels.
Overtime, they grew strong and held dominion over all of Hell, with Lucifer as its ruler and Satan being second in command. Eventually, Satan began retaliation against God by tempting humanity to sin. As such, each of the Seven Princes became the physical representations of the Seven Deadly Sins being: Pride, Sloth, Greed, Gluttony, Wrath, Envy, and Lust.
After the War of Heaven, the imprisoned fallen angels decided they needed a form of ruling government in their new plane of existence. Some vied for power, but undoubtedly, the ruler of Hell at the time was the leader of the fallen angels, the charismatic Morning Star, Lucifer. Courageous and strong, he made others bow before him through persuasion, bribery, or intimidation.
For years, Hell has been organized by Lucifer into the ruling body called the Seven Princes, in which the leading seven would rule over different, vast areas of their lands. Each Prince was responsible for their own subjects and lands. Many enjoyed how organized this system was, though a select few hated being forced at the bottom for their others to be on top.