Mark Hamill and Carrie Fisher
“Star Wars: The Last Jedi” star Mark Hamill said that he and Carrie Fisher were “more like siblings“ than he initially thought. Pictured: Hamill and Fisher attend the Midnight Mission’s 100 year anniversary Golden Heart Gala held at the Beverly Wilshire Four Seasons Hotel on Sept. 30, 2014 in Beverly Hills, California. Araya Diaz/Getty Images for The Midnight Mission

Mark Hamill made his first appearance on “The Ellen DeGeneres Show” on Tuesday to promote his upcoming film “Star Wars: The Last Jedi.” During the interview, host Ellen DeGeneres brought up Hamill’s late co-star Carrie Fisher, prompting the actor to open up about his relationship with his onscreen twin sister.

“She’s like an irreplaceable member of the family,” Hamill said of Fisher who died last December. “The whole world feels that way. We are all sort of mourning her.”

“I always think of her in the present tense,” added Hamill of Fisher who played Princess Leia in the “Star Wars” film series. “I don’t think of her in the past because any time you were with her it was just fun. That’s why it’s so great that [her daughter] Billie Lourd is in the movie because you have that sort of continuity there.”

Hamill, who plays Luke Skywalker in the epic space opera franchise, said that Lourd is so similar to her mother. “They asked me how is she similar to Carrie, and I said, well for start, she’s an hour and a half late to the airport,” the actor joked.

Hamill went on to say that he and Fisher were just as much brother and sister in real life as they were in the film franchise. “Carrie used to drive me crazy,” Hamill said. “We were more like siblings than I thought, because we would have these huge fights. We wouldn’t see each other for months or even years, and then you would see each other and remind yourself how much fun it was to be together because not only could she make me laugh, but I could make her laugh. That was our goal.”

Fisher will still appear alongside Hamill in next month’s “Star Wars: The Last Jedi,” as she completed filming all her scenes in the Rian Johnson-directed movie before her passing. But Hamill previously said that fans of the space franchise will miss Fisher more than ever when the yet-to be-titled “Star Wars: Episode IX” hits theaters in 2019.

“Usually her timing was exquisite, but among the reasons it’s terrible that she won’t be with us is that she was the pivotal character [in that film],” Hamill said (via The Hollywood Reporter) during the In Memoriam segment of this year’s Tony Awards. “And I also look at it selfishly: She was just hilarious. Sometimes I wouldn’t want to go out and do certain things to promote [‘The Force Awakens’], but then I’d find out Carrie would be there, and I’d say OK, because then I knew it would be fun.”

Last April, Lucasfilm president Kathleen Kennedy spoke about Princess Leia’s supposed role in “Star Wars: Episode IX” on “Good Morning America.” “We have not read a script yet [for ‘Star Wars: Episode IX’],” Kennedy said at the time. “Obviously, when Carrie passed away in December, that was a huge blow for all of us and it caused us to sit with [the film’s former director] Colin [Trevorrow] and really rethink where we’re headed with ‘Episode IX.’ Carrie was a significant part of that story — that was something she very much wanted and we very much wanted. But given the circumstances, we would not carry on with that.”

“Star Wars: The Last Jedi” opens in theaters on Dec. 15, while “Star Wars: Episode IX” is set to be released on Dec. 20, 2019.