How normal is sibling-on-sibling savagery? It’s a question I asked myself last week while watching two small children fight, Mike Tyson-style, on Instagram Reels.

The kids, maybe four and two, wore boxing gloves and squared off on a grippy, padded floor. The older sister was thumping her brother like her life depended on it. His retaliation attempts, while honourable, were largely futile – age was on her side. Still, his spirit didn’t break. Every time she totalled him, he got back up, ready for more.

It was addictive to watch – not just for their agility, but because it transported me, like a whiff of forgotten perfume, to my childhood.

Growing up, my older sister was my archnemesis. I can pinpoint the moment it began: my fifth birthday. I went to the toilet and, when I came back, all of my friends were gone from the lounge room. I panicked. Had they gone home? Without saying goodbye? No. Worse. They were in my sister’s bedroom, hanging out with her instead of me. My heart sank. I knew I’d lost them. As any younger sibling will attest, you’ll never be more entertaining than an older sibling with a cooler room and a lava lamp.

Her version of our villain origin story would read differently. She’d probably say it started when I stole her Motorola Razr, opened the “voice recordings” folder and found a clip of her breathily singing Jessica Simpson’s With You. It was the kind of blackmail material a younger sibling........

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