The pair were revealed to be twins later in the trilogy, but fans were completely unaware of the twist to come when Star Wars: A New Hope was released in 1977. Interestingly, it seems even George Lucas himself was unaware of where his story would go at the time. An old copy of the screenplay has the giveaway.
A fourth draft of the script, issued in January 1976 and resurfaced by a fan on Reddit, indirectly lets slip that Luke and Leia weren’t initially expected to be twins.
When we first meet Luke, Lucas’s text reads: “A death-white wasteland stretches from horizon to horizon.
“The tremendous heat of two huge twin suns settle on a lone figure, Luke Skywalker, a farm boy with heroic aspirations who looks much younger than his eighteen years.”
Earlier in the script, when we meet Leia, the script says: “A familiar clanking sound attacks Threepio’s attention and he spots little Artoo at the end of the hallway in a smokefilled alcove.
“A beautiful young girl (about sixteen years old) stands in front of Artoo.”
Giving away that Luke was originally envisaged as being two years older than Leia implies that Lucas hadn’t got the twins twist in mind just yet.
It wasn’t until The Empire Strikes Back, the sequel, that fans learned Vader is Luke’s father.
Then, in Return of the Jedi, we finally learn that Leia is his twin sister.
That is confirmed in the prequel trilogy’s finale, Revenge of the Sith, when we see Padme (Natalie Portman) giving birth to twins, naming then Luke and Leia, and having them separated.
In the wake of actress Carrie Fisher’s death, Mark Hamill revealed her brilliant reaction to finding out the plot point.
“So I remember too when they took us aside and said, ‘ok nobody knows but in this episode you’re going to be revealed as brother and sister,” he told The View.
“And we were sort of shocked – and I thought for a minute, ‘wait, if Luke is Leia’s brother – does that make me royalty?’ And she went, [snapping] ‘NO!’”