Penelope Disick, 3, and North West, 2, were all smiles as they held up Khloé Kardashian's new book
Credit: Courtesy Khloe Kardashian

Khloé Kardashian has two very tiny, very adorable fans: her nieces!

Kardashian took to Instagram on Thursday to share an adorable picture of her sister Kourtney Kardashian‘s daughter Penelope Disick with Kim Kardashian West‘s daughter North West.

“I can’t stop smiling when I look at this photo! I love my little ladies!!” Kardashian, 31, wrote as the caption to the sweet photo of Penelope, 3, and North, 2, grinning widely as they hold up a picture of Kardashian’s new book, Strong Looks Better Naked.

“They were so excited and kept screaming ‘KoKo!’ ‘KoKo!’ North calls me ‘KoKo Loco,’ ” Kardashian added.

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Kardashian, who canceled book signings on Wednesday, is currently recovering from a staph infection she contracted while caring for her estranged husband Lamar Odom at his hospital bedside.

“She’s home on antibiotics and being closely monitored a doctor,” a source told PEOPLE Thurday, adding that “it was exacerbated by stress.”

Another source said Kardashian is recovering well: “She just needs some medication and some rest and she will be fine.”