"What’s mine is yours," the reality star wrote alongside a pic of Penelope wearing a white two-piece, sunglasses and a black hat and climbing the steps on their yacht. Meanwhile, Kourtney is in a white one-piece and looking at her mini-me.
The picture didn't go unnoticed by Kourtney's family. Her sister, Khloe, replied to her post, teasing her about not being around when she's in Los Angeles.
"Are you lost at sea?" Khloe wrote, before adding a second comment. "I come back in town and you leave the next day. Should I catch a hint?"
But Kourtney is living her best life with her three kids and boyfriend Younes Bendjima on their overseas getaway. Earlier in the day, the mother of three posted an adorable Instagram story of Mason, 8, and Reign dancing along to John Mayer's "New Light."
While the rest of the Kardashian sisters are missing out on their Italian vacation, Kourtney and Kim had a blast in Turks and Caicos in April. See more of their trip in the video below.