The ancient Alcmaeonid family was a powerful and influential Athenian family who claimed to be descended from the legendary figure Alcmaeon of Croton, one of the most profound natural philosophers and medical theorists. He was referred to as “a thinker of considerable originality and one of the greatest philosophers, naturalists, and neuroscientists of all time.”
In 631, a man named Cylon wanted to become the tyrant of Athens. (Note–tyrant in Ancient contexts does not bear the same definition that it did in Classical settings. In Ancient Greece, it just meant took power without a vote and did not necessarily imply corruption.) The Alcmaeonid family was opposed to Cylon becoming the tyrant of Athens, and so a fight occurred between Cylon and many other wealthy men of Athens. At the culmination, Cylon gave up and surrendered, thus declaring a truce of peace. However, after this truce members of the Alcmaeonids still proceeded to stab him to death.
This killing under truce resulted in the belief that the Alcmaeonids and all their descendants would be cursed, and thus to protect the city they were all banished from Athens. However, this did not keep them out. They continued to thrive and be a wealthy and influential family although all the Athenians believed that they were cursed.
In 548 B.C. a terrible earthquake occurred in Greece and destroyed the temple of Apollo at Delphi, where the oracle was housed. It was believed by many that this natural disaster was a result of the curse put on the Alcmaeonid family, and thus the family paid to rebuild the religious locus.
Of course, this move and willingness to pay to reconstruct the temple got the Alcmaeonid family on better terms with the Oracle. This paid off for future years to come and helped give the family a redeeming chance in Athens. For instance, Cleisthenes, a general descended from the family, wanted to get in power, so the Oracle encouraged the Spartans to help overthrow his opponent. The Oracle as well supported the ascent of Pericles and perhaps even made it possible.
The last famed Alcmaeonid was Alcibiades, who was the nephew of Pericles. Fulfilling the earlier prophecy and curse, he betrayed Athens which resulted in the loss of the Peloponnesian War in 404 B.C..