Powerful+Three

Zeus, the god of the sky Posiden, the god of the sea Hades, god of the Underworld

The Big Three are the three main gods that rule the world. Zeus rules the sky, Posiden the sea, and Hades's domain is the Underworld. After World War II, the Big Three made a pledge to not have kids, but Posiden and Zeus broke there pledge be having Percy(Posiden) and Thiala(Zeus).