Big Three

The Promise is a deal made by the Big Three gods, Zeus, Poseidon, and Hades, after World War II. Because the war was started by powerful demigods, they vowed to have no more children. Zeus was the first to break the Promise, giving birth to Thalia. Next to break the promise was Poseidon, who fathered Percy Jackson. Although Hades did not technically break the Promise, two of his children, Bianca di Angelo and Nico di Angelo, spent time in the Lotus Hotel. They came out after World War II, although they were born before it. In all, there are three demigods who are sons or daughters of the Big Three, since Bianca is now dead.