Poseidon was one of the three sons of the Titan Cronus and his sister, Rhea. This made him the brother of Zeus, Hades, Hestia, Demeter, and Hera.
Like his other siblings, aside from Zeus, Poseidon was swallowed at birth by his father. Hoping to ensure that he would never lose power to one of his children, the king of the Titans tried to ensure that they would never grow to challenge him.
He failed in this, however, because Rhea and Gaia hid the infant Zeus from him. Zeus’s first action when he was grown was to free his brothers so they could fight by his side.
Poseidon and his brothers were very similar in both their personalities and the ways in which they were depicted. Rather than being just because they shared parents, this was also because of the ways in which the characters developed when Greek religion was in its infancy.
Poseidon was, like Zeus, a son of Cronus and Rhea.
His father was the youngest of the Titans. Despite this, Cronus became the king of the gods because he was the one to overthrow his father, Uranus.
Cronus married his sister, Rhea. Although they had many children, Cronus endeavored to make sure none would grow into adulthood.
Gaia, the Mother Earth, had warned her son that one of his children would someday defeat him just as he had his own father.
To prevent this, Cronus swallowed each of his children as soon as they were born. His three daughters were first, Hestia, Demeter, and Hera, followed by two sons, Poseidon and Hades.
Only Zeus was spared, because his mother and Gaia hid his birth. Cronus was tricked into swallowing a stone instead, and his youngest son grew up in hiding.
When Zeus was grown, he returned to challenge his father. His first act was to disguise himself as a cupbearer to free his siblings.
With the help of a Titaness, Metis, Zeus gave his father a powerful purgative. The potion induced vomited, causing Cronus to expel his children from his stomach.
Poseidon and Hades joined their brother in his rebellion.
The three brothers led a coalition of younger gods and allies in the Titanomachy, the war against the Titans. Eventually they, like the Titans before them, defeated the older generation of gods and took power for themselves.
After the Titan War had ended, Zeus did something different than his father. Instead of claiming kingship solely for himself, he shared power with the brothers who had helped him win the war.
While Zeus was the king of the gods, each of the brothers took a realm for themselves. They also shared power on Earth, as no single god could claim power over Gaia.
Zeus took the sky for his realm, while Hades took the Underworld. Poseidon became the god of the sea, second only to his younger brother in overall power and authority.
Poseidon’s position in the Greek pantheon was strengthened by the fact that he was the brother of Zeus. While each god and goddess of Olympus was powerful in their own right, Zeus and his brothers were recognized as rulers over all of the others.
Rather than having domain over a specific aspect of life, each of the sons of Cronus ruled over an entire realm. This gave them authority not only over mankind, but also over the other deities that operated within their sphere of power.
Zeus had been named the king of all the gods, but in most instances, Poseidon was his near-equal. The three lords of the gods shared not only a family of origin, but also a level of authority.
Poseidon and Zeus, and to a lesser extent Hades as well, were very similar gods. They were depicted in virtually identical ways, were said to have similar personalities and temperaments, and their powers sometimes overlapped.
Both Poseidon and Zeus, for example, were notorious for being quick to anger and violent in their wrath. Both took many mistresses, and in different traditions there was often confusion over which of the brother fathered certain figures.
The similarities between the gods were often explained by their shared ancestry. As brothers, Zeus and Poseidon could be expected to be relatively similar.
Other sibling gods, however, did not share the same close affiliation as the sons of Cronus, however. Zeus’s own sons, for example, are easy to distinguish in art, have much more varied personalities, and often have little crossover in their mythology.
Instead, the similarities between Poseidon and his brothers may be due to the shared origins of their characters outside of legend.
One explanation favored by some historians is that the three chief Olympians were originally one deity.
The three figures of Zeus, Poseidon, and Hades represented three different functions of a supreme ruling god. In his different aspects, this god ruled over the sky/heavens, the Earth/sea, and the Underworld.
As mythology became more complex, these three aspects were separated into three distinct, but still similar, gods. In Greece, this may have been aided by the fact that the mythology was influenced by outside religions.
Zeus is believed to have been the most powerful deity of the earliest Greek-speaking people. When they moved into the region they would come to control, they encountered native religions and were introduced to other pantheons through trade and expansion.
It is well-documented that many Greek gods belonged to indigenous cultures and were assimilated into Greek religion. Many historians believe that Poseidon was one of these.
Echoes of the ancient Minoan culture are found, for example, in the Greek myths set on the island of Crete. In these, Poseidon is more active than his brother, Zeus.
An additional piece of evidence is Homer’s Odyssey. The story is believed to have been passed down through oral tradition for generations before Homer’s time and features Poseidon, rather than Zeus, as its primary god.
These examples show that, before the introduction of Zeus, the god who would become known as Poseidon was the chief deity of the region. In some cases, such as the story of Europa’s abduction to Crete, the original god was recast as Zeus, but in others Poseidon retained an outsized importance.
Whether Poseidon and Zeus were once aspects of the same divine power or whether Zeus simply supplanted a local deity, the reaction in mythology would be to continue their connection. By making them both sons of the previous king, this connection was maintained and their similarities were justified.
Being sons of the deposed king also gave their power legitimacy. Just as Zeus was the undisputed king for having taken the throne, Poseidon too was an heir of Cronus.
Poseidon was the son of Cronus, the king of the Titan gods, and his sister and wife Rhea. Cronus swallowed each of his children shortly after their birth to ensure that none could ever grow to take his position for themselves.
Rhea, however, hid her sixth child. Zeus would grow up in secret and return to challenge his father.
The first step in Zeus’s ascent to power was to free his siblings. Poseidon and Hades, once disgorged, joined their brother in the war against the Titans.
The three sons of Cronus took control over separate realms, sharing the Earth, but remained very similar. In both personality and imagery, the brothers had a close resemblance.
Historically, there are reasons for these similarities beyond their role as brothers.
All three gods may have once been aspects of the same powerful deity. Over time, the gods’ functions were separated to create three unique rulers who still shared many characteristics.
An alternative explanation is that Poseidon may have held a similar position to Zeus in a pre-Greek culture. Evidence in early written mythology and from the Minoan culture of Crete supports the idea that Poseidon was the chief god of an earlier pantheon.
With the arrival of the first Greeks, and Zeus as their most powerful god, Poseidon was put in a position below the sky god in the new hierarchy. Because they had both been kings, however, they maintained certain similarities in how they were perceived.
In making Poseidon and Zeus both sons of Cronus, the sea god’s position of power was legitimized and explained. As the son of the former king and the brother of the current one, Poseidon’s prominence and his similarities to Zeus became part of a family legacy.