North West and Penelope Disick have their own language that’s almost too adorable

North West and Penelope Disick aren’t just cousins, they’re best pals. While celebrating Disick’s fourth birthday on Friday, Aunt Kim Kardashian took a video of the two besties communicating/singing in their own secret language — and it’s almost too adorable to handle.

“Whatever secret language u girls speak, the way you girls protect each other & love each other is so special,” Kardashian captioned the video. “Penelope, North is so lucky to have a best friend like you! Happy Birthday my sweet P. I love you to the moon and back!”

Disick is celebrating her birthday in the Bahamas with her mom and friends. Kourtney Kardashian posted this sweet message to her daughter: “Happy birthday to my little mermaid! Seeing the magic in the world through your eyes makes me so happy.”

North West’s third birthday was on June 15, and the cousins had a joint mermaid-themed birthday party that rivaled all mermaid birthday parties everywhere. Seriously, these two can’t get enough with the mermaids! We wonder if that new language of theirs make sense if you listen to it underwater, a la the merpeople in Harry Potter.