A party for two! North West and Penelope Disick celebrated their birthdays at a joint mermaid-themed party on Saturday, June 18.

North, who turned 3 on June 15, and Penelope, who turns 4 on July 8, looked adorable in matching costumes inspired by The Little Mermaid as they partied with the rest of the Kardashian-Jenner clan.

Clad in a pink wig, Khloé Kardashian posted hilarious videos with sister Kylie Jenner and Kourtney Kardashian’s ex, Scott Disick, on Snapchat. In the clips, she jokes about being “Becky with the pink hair” — in reference to Beyoncé’s recent hit “Sorry” — and quips, “Normally it’s Kylie in a wig!” Khloé later admitted on Instagram that her nieces had asked her to wear the lavender wig.

Kim Kardashian also got dressed up for the occasion in a white and green costume, which she paired with a long pearl necklace.

Inside the house, Kim, 35, and Kanye West watched as their daughter sat on the kitchen counter alongside Kourtney and Scott’s daughter. The cousins excitedly flipped their mermaid tails as they each blew out the candles on their individual cakes, which were also, naturally, decorated with beautiful mermaid trinkets and shells.

At one point, Khloé, 31, hopped onto the counter and posed with the birthday girls and Penelope’s older brother, Mason.

Earlier in the week, Kim kicked off North’s birthday with an adorable Instagram video, which teased the theme of Saturday’s event.

“She promised me she wouldn’t get any bigger!” the reality star captioned the post. “I can’t believe my baby girl is 3 years old today!!!! Northie I love you so much I can’t even explain it! Happy Birthday to my favorite mermaid!!!”

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