In the world of Netflix blockbusters, few pairings are as charming as Millie Bobby Brown and Henry Cavill in the Enola Holmes franchise. Playing the spirited Enola and her stoic older brother Sherlock, the duo displays a natural, bickering chemistry that fans adore. However, as Millie revealed during the press tour for the series, their off-screen dynamic is governed by a set of “terms and conditions” that would be unthinkable on the set of Stranger Things. While Millie is used to the boundary-free, sibling-like chaos of the Hawkins crew, the man who played Superman established a firm “boundary wall” when it came to his private life.

The Contrast: “Schoolmates” vs. “Adults” Millie Bobby Brown has spent over a decade growing up alongside Noah Schnapp, Finn Wolfhard, and Charlie Heaton. On the Stranger Things set, privacy is almost non-existent. “There are no boundaries because it’s like we’re all siblings,” Millie told Deadline. “I met them when I was 10. So for me, it does feel like schoolmates.” With Henry Cavill, the dynamic shifted toward what Millie calls a “real adult relationship.” Despite their 21-year age gap, the two formed a healthy, supportive bond—but it came with a list of “unwritten rules” designed to protect Cavill’s notoriously guarded personal life.

The “Shut Up” Rule Henry Cavill is one of Hollywood’s most intensely private stars. Whether it is his relationship with producer Natalie Viscuso—with whom he recently welcomed his first child in early 2025—or his personal hobbies, Cavill rarely offers up details for public consumption. Millie quickly learned that prying into his love life or personal affairs was strictly forbidden. Millie admitted she is simply not allowed to ask about his personal life. Whenever she gets too “pesky” or nosy, Cavill is quick to set her straight. “It’s like, ‘Millie, shut up. No.’ And I’m like, ‘Understood,’” she joked. Cavill, who has four brothers and no sisters, initially found Millie’s high-energy nature “shocking,” requiring her to pull him out of his comfort zone to build their sibling chemistry.

Notable Events: Pranks and “Drunk Sherlock” Despite the strict boundaries, the two share a playful rapport that relies on professional respect and mutual teasing. During the filming of the first Enola Holmes, Millie constantly teased Cavill with the threat of making him do a TikTok dance. Cavill’s “punishment” for this came in the sequel, where he had to play a drunken Sherlock. In Enola Holmes 2, there is a scene where Enola helps a drunken Sherlock walk home. Cavill admitted to BBC Radio 1 that he intentionally leaned “heavily” into Millie during those takes as revenge for her past jokes. “There were certainly times where she was like, ‘There’s no way I could actually hold you up!’” he recalled.

A 2025 Legacy: Final Wraps and New Chapters As of December 2025, the bond between the two remains deep but professional. Following the wrap of the upcoming Enola Holmes 3, which took the mystery to Malta, the pair have solidified their status as a premier on-screen duo. Meanwhile, Millie has officially closed the book on her childhood era. On December 7, 2025, she appeared on The Tonight Show and revealed she made 30 handmade friendship bracelets as wrap gifts for the Stranger Things cast, marking the emotional end of her “no boundaries” schoolmate dynamic. For Millie, Cavill’s strictness was a pivotal lesson in professionalism, providing a “healthy” model of adult friendship as she steps into a more mature phase of her career.