North West & Penelope Disick Support Their Naked Aunt Khloe Kardashian

There's nothing sweeter than little kids who love their family -- even when said family member is posing nude on the cover of a book the kids aren't even old enough to read.

Khloe Kardashian shared an impossibly adorable photo to Instagram on Thursday, showing her nieces Penelope Disick and North West holding her new book Strong Looks Better Naked

WATCH: Khloe Kardashian Poses Completely Nude for Cover of Her New Book, 'Strong Looks Better Naked'

"I can't stop smiling when I look at this photo! I love my little ladies!" Khloe captioned the cute snapshot. "They were so excited and kept screaming 'KoKo!' 'KoKo!' North calls me 'KoKo Loco.'"

WATCH: All the Times North West and Penelope Disick Were Totally Adorable BFFs

It's hard to pinpoint what aspect of this photo is the cutest: 3-year-old Penelope and 2-year-old North's carefree smiles, or that, as little kids, they look like they don't quite understand how to hold a book.

The 31-year-old Keeping Up With the Kardashians star has been busy promoting her best-selling book, but recently had to cancel a stop on her publicity tour after coming down with a "minor infection," a source recently told ET.

WATCH: Khloe Kardashian's New Book Sheds More Light on Lamar Odom's Drug-Addled Past

Check out the video below for a look at some of the candid revelations Khloe shares in her new memoir.