AceShowbiz -

Kendall Jenner and Kylie Jenner talk about their biggest fear in a latest magazine interview. Kendall is only 19 and Kylie is 17 but the sister duo is already worried about ageing. Kendall says living a "fast-paced" life terrifies her while Kylie wishes she could be teen forever.

"I'm scared of the day I turn 19," Kylie said as quoted by The Sunday Times' Style where they graced the cover together for the latest issue. "I really don't want to grow past 18." Looking at her sister Kendall, she added, "You'll be 20 this year - that's crazy. And any second you'll be, like, 21, 22, 23..."

First look! Kendall + Kylie Jenner on the cover of today's @theststyle chatting about their exclusive #Topshop collection! Don't miss the drop, Wednesday 3rd June! @kendallandkylie @kendalljenner @kyliejenner #Kendalljenner #kyliejenner #topshopstyle #collection #fashion #ss15

A photo posted by Topshop (@topshop) on May 31, 2015 at 6:11am PDT

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The older sister agreed as she chimed in, "It's scary. Life is scary. It's just scary how fast everything is rolling and you can't stop it. It's rolling right now. You see a picture and you've changed so much in a year." Kylie added, "I've done so much, physically and whatever."