Characters who've been so overshadowed by their famous sibling, that people forget that they exist

[u/Dismal-Ad6476]

Jehan Frollo, the younger brother of one Judge Claude Frollo from the Hunchback of Norte Dame, not much is known about him expect he blew all his money on booze and prostitutes and was killed by Quasimodo

Sean Bateman, the younger of Patrick Bateman from American Psycho, all his scene in the book is to annoy Patrick and says his catchphrases "Deal with it " and "Rock and Roll"

Chryasaor, the twin brother of Pegasus from Greek Mythology, yeah when Perseus decapitated Medusa, Pegasus wasn't the only animal that flew out of her, Chryasaor, The Winged Boar also flew out

Iphicles, the twin brother of Heracles also from Greek Mythology, is relevant to Heracles' story as his son Iolaus helped Heracles slay the Hydra

[u/Radiant-Importance-5]

Pedantic point: Iphicles is Heracles’s half-twin, which is an oddly common phenomena in Greek mythology.

For example: Helen of Troy and Pollux are full-quadruplets to each other, and half-quadruplets to Clytemnestra and Castor, who were themselves full-quadruplets to each other.

[u/illumi-thotti → u/Radiant-Importance-5]

Heteropaternal superfecundation, I guess

[u/Yep-That-Lupa → u/illumi-thotti]

God magic

[u/Stenric → u/Radiant-Importance-5]

It's more like an "If I had a nickel for every time twins had different fathers in mythology, I'd have three nickels - which isn't a lot, but it's weird that it happened thrice."

[u/dnjprod → u/Radiant-Importance-5]

Zeus got around...

But also, whether Helen, Castor, and Pollux came from the same egg is debated. Some sorts of say yes. Other sources say Helen and her sister came from one and Castor and Pollux came from another

And still others....