Via Starwars.com:

In ancient times, twins were a subject of curiosity. Perhaps society didn’t understand the science of birthing twins, or perhaps they were an easy comparison to the strange duality of the universe, but they have always been a large part of ancient and modern mythology.

Definition: Twins in Mythology

Another name for twins in mythology is dualistic cosmology, because the twins motif is not restricted to blood twins. In some cases, they are considered twins because of commonalities between them. In some cultures, for example, two people could be considered twins if born on the same day. In mythology, the twins’ relationship is usually complementary; they are different but the same, and almost always rivals or partners. Either way, they are usually portrayed as being two halves of a whole.

Twins in mythology are often used to describe the duality of nature, whether it be the sun and moon, male and female, winter and summer, etc. Mythological twins were often attached to these forces of nature as a way to explain them. Sometimes they are at odds with each other, and sometimes they work together as equal partners. This is the fundamental nature of twins in mythology.

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