Prometheus warned Epimetheus not to accept gifts from Zeus in Pandora’s story.
Prometheus is a Titan famous for helping humanity and stealing fire from the gods. In Hesiod’s account, he recognizes that Zeus’s gift of Pandora is dangerous and advises his brother Epimetheus to reject it. Epimetheus ignores the warning, and Pandora later opens the vessel containing the evils.
The warning fits Prometheus’s traditional role as a figure of forethought. His name is commonly connected with thinking ahead, while Epimetheus’s name is associated with thinking afterward. The contrast gives the family relationship a clear narrative function rather than making the two brothers interchangeable.
Prometheus’s fire theft and Pandora’s creation are closely connected in Hesiod’s Works and Days: Zeus responds to humanity’s benefit from stolen fire by arranging a new punishment. Later retellings may rearrange the events, but Prometheus remains the brother who gives the warning.