Dash Barber played the titular monarch's grandson in the Peter Morgan-directed film about Queen Elizabeth II's handling of Princess Diana's death.
King Mustafa's murderous younger brother, voiced by Jeremy Irons, wasn't even content to be first in line, let alone second once nephew Simba arrived.
He finds himself in the spotlight and next in line after his dashing, bred-for-the-throne older brother dies suddenly.
Redhead Henry Holland got the call to play Diana's younger son in the widely panned biopic.
The infamous king, played in his never-quite-so-studly youthful glory on the Showtime drama by Jonathan Rhys-Meyers, was actually a spare, but his older brother, Arthur, Prince of Wales, died at the age of 15.
As the second brother, Queen Elizabeth II's father, whose born name was Albert, never planned on being king. But then Edward, Duke of Windsor, abdicated to marry American divorcée Wallis Simpson, so... Besides, Colin Firth was way more cuddly than Guy Pearce anyway!
The made-for-prime-time drama that was the Egyptian monarch's actual reign was majorly simplified for the 1963 film, but in real life Ptolemy XIII married his older sister, Cleopatra, so his birth order was win-win for him! Richard O'Sullivan remained on the sibling sidelines in the film, while Rex Harrison's Julius Caesar rules with Elizabeth Taylor.
Speaking of incest... The younger brother of equally towheaded Prince-turned-King Joffrey is at least a spare heir as far as he knows. Dean-Charles Chapman assumed the throne, er, role in the HBO hit's fourth season, replacing Callum Wharry.
Robert Shaw's version of the much-married monarch in the 1966 classic earned him an Oscar nomination for Best Supporting Actor.
Yes, technically the baby boy whom the pharoah's daughter found floating in the river in a reed basket was not a spare heir by blood. But in the Cecil B. DeMille classic he was treated like a royal son until the pharoah died, Rameses assumed the throne and... You know, Passover. Ultimately Moses moved on to much bigger things.
Also a spare heir, Henry VIII's younger daughter became queen after half-sister Queen Mary I (aka "Bloody Mary") died. Helen Mirren wore the crown for this 2005 miniseries and ended up winning Golden Globes for both this and playing Queen Elizabeth II in The Queen—for the same year!
It's not always easy being Elsa's little sister, especially when the Snow Queen is accidentally freezing your heart—but all is thawed out by happily-ever-after time!
Cate Blanchett goes to bat as the Virgin Queen once again in this 2007 sequel to 1998's Elizabeth.
Of course, it turns out that the scene-stealing Tom Hiddleston isn't really Chris Hemsworth's brother, all the better to mastermind an elaborate plot to prove himself worth to adoptive father King Odin.
NEXT GALLLERY: Spare Heirs: Second-Born Royal Siblings