Twins figure into a lot of those. You have Esau and Jacob, Romulus and Remus, Apollo and Artemis, Quetzalcoatl and Xolotl, Jaime and Cersei…
I’m a huge fan of all kinds of myths–I’ve read everything from Celtic and Scandinavian myths to South American and African myths. And if you like the tale of Hunahpú and Xbalanqué you might enjoy a book called Barbecued Husbands, a collection of folk tales from Amazonian tribes. I remember a particularly lovely story about a brother and sister who are captured by the Jaguar people.
But my favorite, easily is, the epic of Gilgamesh. I first read it shortly after losing a very close, very old friend–someone who joked that she and I knew each other from birth. After the loss of Enkidu Gilgamesh goes through the five stages of grief. First there’s anger, then denial, then depression, as expressed here:
When he had gone one double-hour,
thick is the darkness, there is no light;
he can see neither behind him nor ahead of him.
This is repeated three times until:
At the nearing of eleven double-hours, light breaks out.
At the nearing of twelve double-hours, the light is steady.
(quoted from Gilgamesh, translated by John Gardner and John Maier, with the assistance of Richard A. Henshaw.)
Finally he goes through bargaining as he tries and fails to achieve immortality and, returning to Uruk, there is acceptance.
For me it’s always going to be Orpheus and Eurydice. It resonated when I first read it at around 9 years old (before I even started screwing up relationships) and has never stopped.
Came for the lingam, didn’t leave dissapoint.
psst… Esau and Jacob were half-brothers.
I don’t suppose the Invisible Hand is old enough to count as mythopoesis?
I think you’re remembering Isaac and Ishmael, a different pair of Old-Testament siblings with complicated birthright issues.
Nope. You’re getting them confused with Isaac and Ishmael. Jacob and Esau are twins, sons of Isaac. It’s easy to get mixed up because (as often happens in ancient mythology) there are a lot of similarities passed from the story of the father to the story of the son. In this case, both Issac and the twins were born to parents thought to be too old, and mothers thought to be barren.
Wooooooops. 
The important thing to remember is that brothers in the Old Testament often weren’t the best of buddies. I guess the first brothers ever didn’t give them much of an example to live by.
My favorite myth is how health insurance companies have our best interests at heart. That one kills me every time. Literally.
When I was little my father told me the Aztec myth about the creation of the mood moon, and why you can see a frightened rabbit jumping on the face of the moon. It’s always been my favorite.
Edit: Moon not Mood, thanks @anon52120741. Although, the mood version explanation you gave is beautifully hilarious.
Yeth?
Benghazi Conspiracy?
Mith Mannerth?
Like @SpunkyTWS, I had a lifelong fascination of mythology from around the world…
I really can’t pick a favorite (something will likely creep into my consciousness later)… As a kid, Roman/Greek mythology, the Norse legends, and Cú Chulainn were faves (Native American tales were also a hit since they often included fart jokes…) As an adult aged child, it is probably mostly the “eastern”, african, pacific, etc myths that catch my interest.
I was always fascinated by the myths that seemed to show up everywhere (and was probably the reason that I, effectively, became an atheist at around the age of 8).
quick edit to add adult blurb
Sisyphus, as seen by Camus
I particularly like the part where Quetzalcoatl tells Tezcatlipoca to put on something more comfortable while he makes drinks, then puts on some Barry White.
Seriously though, I’d probably go with any of the Greek gods, such humanity in a lot of their stories about these vast outsized people that humanity has been ignoring any semblance of behavior for thousands of years.
I just get amazed at how we all refuse to learn from past mistakes because “It’ll be different this time!” and suddenly we’re shocked when everyone always wants to look back to see if their love is following them out of Hades or that self love can lead to destructive behaviors.
After experiencing much hilarity at http://www.bettermyths.com , they’ve all started to blend together a little.
(I suggest starting with a “Myth Chosen by Fate”, as the author has been branching out into other things lately. Not that his take on The Simarillion is any less worthwhile.)
How ironic, considering that Maggie Koerth-Baker would follow this with a story asking why scientists focus more on the lingam than the yoni.
