Popeye has four nephews: Pipeye, Peepeye, Pupeye, and Poopeye.

Despite his engagement to Olive Oyl, Harold Hamgravy was often attracted to other women who were considerably wealthy. Hamgravy was depicted as a slacker who preferred getting rich quick over earning money honestly. In a later strip, Hamgravy hired a sailor named Popeye to man his ship for a treasure hunt. Intended as a minor supporting character, Popeye proved so popular that he was made a permanent member of the main cast, and as time passed, he replaced Hamgravy as the object of Olive's affections.

Popeye wasn't always a spinach fanatic. In early stories from the Thimble Theatre comic strip, the sailor gained his special powers by rubbing the hairs on the head of a magical Whiffle Hen named Bernice. In fact, Popeye almost dies in his inaugural adventure, only to recover from otherwise fatal gunshot wounds by rubbing Bernice's head.

In the comics, Swee'Pea is a baby left on Popeye's doorstep. Popeye adopts and raises him as his son, or, as he puts it, "boy-kid". Initially, Swee'Pea's speech consists entirely of the sound "glop" but he eventually ages enough to speak normally and can even throw punches if he has to. In the cartoons, Swee'Pea is usually depicted as Olive Oyl's cousin or nephew that she has to take care of from time to time.

Castor Oyl, Olive Oyl's older brother, debuted in Thimble Theatre on January 14, 1920. He was the protagonist of the strip for years before the first appearance of Popeye in January 1929. A quick-witted yet diminutive adventurer, Castor Oyl continued to be an important character in the Popeye strip, but played virtually no role in the Popeye theatrical cartoons.