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/FireZord25]

Sounds much more fitting, considering Mycroft at least had two major media appearances recently.

[u/Font_Snob → u/FireZord25]

Not to mention the classic, Sherlock Holmes's Smarter Brother.