Oh wow, this is one of those topics that makes you raise an eyebrow but also kinda hooks your curiosity, you know? I’ve stumbled across a few films that dance around this theme, though they usually frame it as taboo or emotionally complicated rather than outright forbidden. Like, 'Closer' isn’t about step siblings, but it’s got that raw, messy intimacy vibe. Then there’s 'The Dreamers'—more about blurred boundaries, but it’s got that tension.
For something closer to the ask, 'Flowers in the Attic' (the 1987 version) is the classic—gothic, twisted, and all about repressed family secrets. The newer Lifetime movie adaptations dialed down the darkness but kept the taboo angle. Honestly, most mainstream films shy away from outright step sibling romance, but indie or foreign flicks sometimes flirt with it. Korean drama 'A Frozen Flower' isn’t step siblings but has that forbidden love energy—super intense and beautifully tragic.