At six, they started opera training to fix a stutter. The real launch came with We Need to Talk About Kevin (2011), playing Tilda Swinton's homicidal son in a film that premiered at Cannes and shook critics awake. The Perks of Being a Wallflower (2012) confirmed it: Miller could walk into a teen drama and immediately own it. DC cast them as Barry Allen in 2014, and the franchise era began. The indie credibility that got them there slowly got buried under a superhero suit.
The Flash (2023) was supposed to be a franchise cornerstone. Instead, it became one of WB's biggest losses. Miller's 2022 spiral did the damage: two Hawaii arrests, restraining orders, and a Vermont burglary charge that got plea-bargained down to misdemeanor trespassing in January 2023. They went quiet, cited 'complex mental health issues,' and disappeared for two years. Probation ended in January 2024. By May 2025, Lynne Ramsay confirmed they'd star in her next film. The talent was never the question.
The stutter that prompted opera lessons at six led to performing with the Metropolitan Opera as a child, which is a genuinely absurd origin story for someone who'd later headline a superhero franchise. Miller also toured with indie rock band Sons of an Illustrious Father for years, well into their DC career. The Lynne Ramsay connection runs deep: Ramsay directed We Need to Talk About Kevin in 2011. That relationship has outlasted everything.