The Hero's Journey is a framework that scholar Joseph Campbell came up with that many myths and stories follow. Many storytellers and story-readers find it a useful way to look at tale. (That's actually putting it lightly. Some people are straight-up obsessed.) Chris Vogler adapted Campbell's 17 stages of a hero's journey, which many screenwriters use while making movies. Vogler condensed Campbell's 17 stages down to 12, which is what we're using. Check out a general explanation of the 12 stages.
"The Dioscuri" doesn't fit perfectly into the Hero's Journey structure, but we're giving it a shot. As the gross old saying goes, there's more than one way to skin a cat.
The Dioscuri live an awesome life of being awesome heroes. It's awesome. Super awesome. Super super super awesome. Okay, that's enough. You get the picture.
Call To Adventure
Adventure calls when Castor and Pollux spot two lovely ladies named Pheobe and Hilaeira.
Refusal Of The Call
There's no refusal of the call at all. The twins see the pair of hotties and go right to business.
Meeting The Mentor
Yeah, this story skips over this step.
Crossing The Threshold
Castor and Pollux thoroughly cross the threshold when they kidnap Pheobe and Hilaeira and force them to be their wives.
Tests, Allies, Enemies
The twins definitely make some enemies by taking these ladies, because the girls just so happen to be engaged to the Dioscuri's cousins Lynceus and Idas. Later on, though, Lynceus and Idas seem like buddies because they go cattle rustling with Castor and Pollux. After some disagreements over who gets to keep the herd of cattle, however, Lynceus and Idas definitely become enemies again.
Approach To The Inmost Cave
When Lynceus and Idas come to Sparta for a visit, Castor and Pollux sneak off to steal the cattle. We wonder if they really know how much danger they're walking into.
Lynceus and Idas catch Castor and Pollux in the act and an awful battle ensues. By the end of it, both Lynceus and Idas are dead, but Castor is mortally wounded.
Pollux begs Zeus to let him share his immortality with his dying mortal brother. The king of the gods rewards his brotherly love by placing them both in the sky as the constellation Gemini.
The Road Back
Yeah, we skip over this step, too.
Though the brothers aren't returned to life, they are given an eternal life in the heavens, which totally fits this category.
Return With The Elixir
The Dioscuri now serve forever as a symbol to all of the power of brotherly love.