It’s the sibling rivalry a decade in the making.

When young Mudgeeraba runner Sienna McDonald crossed the finish line at last year’s Gold Coast Airport 5km Fun Run she became the youngest competitor to join the Gold Coast Marathon 10 Year Club.

At 10 years and 143 days of age it was a record that you might ordinarily think might take some time to beat.

But her fleet-footed little sister Harper has other ideas and dutifully abiding to the ‘anything you can do I can do better’ principle she’ll shave Sienna’s record by 66 days when she runs her own 10^th Gold Coast race on Saturday 1 July.

And she’s not shy about letting her big sister know.

“I’m really excited to break Sienna’s record; it’s always fun when you beat your older sister,” Harper said with a cheeky little sister smile.

“Doing the 5km has been a family tradition since my mum [Katie] and my grandparents used to push me in the pram. We used to always finish near the back, but last year I ran more of the race.

“This year I’m doing the race with my mum and sister again and I’m hoping to do my fastest time, and I’m looking forward to getting my tenth running medal,” she said.

Despite her pocket rocket record breaking feats on the streets of the Gold Coast, Harper also finds time to hone her sporting prowess in other areas.

“Running isn’t really my favourite thing, I’m better at netball and swimming,” she said.

And of course, there’s the matter of proper post-race sustenance.

“I just hope they have some good snacks in the 10 Year clubhouse.”