The starry cast of an upcoming film are receiving backlash over a threesome scene involving Orlando Bloom and his co-stars and real-life sisters Rooney and Kate Mara.

The movie, titled Bucking Fastard and directed by Werner Herzog, includes a sex scene in which Bloom’s character gets intimate with the real-life siblings, who also play sisters in the film.

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The provocative set-up, particularly given that the Mara sisters are actual relatives offscreen, sparked debate after Bloom described the “very sincere” threesome during a recent festival appearance, with folks sounding off on his comments on social media.

“This is just weird,” one onlooker wrote on Reddit, while another added; “What the f**k is happening? Why would the Maras agree to this?”

Others chimed in with similar sentiments, saying “It’s weird to act out a sex scene with your sibling,” wither others adding they were “appalled” and “shocked they would actually do this.”

“My gut feeling is that it was unethical to even invite real-life sisters to act such roles,” another Reddit user quipped. “Talking about incest like it’s poetic is gross.”

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Others were less outraged by the movie’s threesome plot point, arguing “it’s all just acting” and that the Mara sisters “are adults” who agreed to take on the roles.

“It seems like there’s a lot of implying what happens rather than seeing it play out in detail,” another defender wrote.

The backlash came after Bloom discussed Bucking Fastard’s “very sincere” threesome scene alongside Herzog at the San Sebastián Film Festival in Spain.

“[There is] such simplicity to the characters and [their] carnal desires, but also an innocence to the sisters,” Bloom said of the Maras’ sibling characters.

Bloom added that his character is “sensitive” and “out of his depth,” including in the sex scene he shares with the siblings.

“[The threesome] was a very sincere sort of moment that was created,” Bloom said.

Herzog added that the scene was a moment where he had to “step back” as a director.

“[I told Bloom], you are in bed, and you have two women in your arms. How you deal with it, I cannot give instructions,” Herzog recalled, describing the scene as “beautiful” with “such charm and depth.”

Bucking Fastard is said to be loosely based on British twins Freda and Greta Chaplin, who became notorious media fixtures in the 1980s for eerily speaking in unison and sharing the same love interest.

Alongside Bloom and the Mara sisters – who are acting together for the first time – the film stars Domhnall Gleeson and Hugh O’Conor, and had its premiere at the Venice Film Festival earlier this month.

It’s not the first time Bloom has made waves with an X-rated moment. In 2016, the actor went viral with a paparazzi shot of him paddle boarding with then-partner Katy Perry while completely nude, and later explained that he didn’t suspect any cameras were nearby so he “had a moment of feeling free.”

Bloom and Perry broke up in July of last year after almost a decade together, with the pop star having since moved on with former Canadian prime minister Justin Trudeau.

The Pirates of the Caribbean star, meanwhile, was recently linked to Luisa Laemmel, after he was spotted leaving the Super Bowl with the Swiss model in February.