Known as one of the great heroes of Greek mythology, Perseus was also Heracles' great grandfather. There are several key similarities between Perseus' and Heracles' journeys. For example, while Perseus rescued the fair Princess Andromeda from being eaten by a sea monster, Heracles rescues the beautiful Princess Hesione from being eaten a sea monster. Andromeda's parents had angered Poseidon, causing them to sacrifice her to the sea god. Similarly, Hesione's parents had ticked off Poseidon, causing them to sacrifice her to the sea god. In both cases, Perseus and Heracles swoop in at the right time and rescue the ladies. Unlike in the story of Perseus and Andromeda, Heracles doesn't marry the princess. Actually, he gives her away to another guy.
Read all about Perseus and Andromeda in our handy-dandy Shmoop guide.