Kylie Jenner Wishes Happy Birthday to Nieces North and Penelope in Instagram Snap

Kylie Jenner and baby Stormi are wishing North West and Penelope Disick a happy birthday in the chicest way possible.

Sunday, Jenner posted a photo with her 4-month-old baby girl, looking casual cool in khaki shorts, an oversized white tee and slicked back hair. Stormi appears to be riding in style in a Gucci carrier.

"happy birthday North & P.. 🖤" Jenner captioned the sweet mother-daughter photo.

Kim Kardashian and Kanye West's eldest child turns five next week, while Kourtney Kardashian and ex Scott Disick's oldest daughter will turn six at the beginning of July.

Traditionally, the two families celebrate the cousins' birthdays at the same time, and this year was no different. The KarJenner family kicked off the party this year early with a too-cute unicorn-themed outdoor birthday party Sunday.

In Kardashian's Instagram Stories, North and Penelope can be seen rocking matching rainbow robes with unicorn horn headbands.

Due to them being so close in age, North and Penelope have been inseparable growing up. Luckily for the Keeping Up with the Kardashians family, there's another group of cousins that will be able to grow up so close.

Jenner's daughter with boyfriend Travis Scott, Stormi, was born just a few weeks after Kardashian's daughter, Chicago West, was born via a surrogate. And just two months after Stormi came into the world, sister Khloe Kardashian gave birth to daughter True with boyfriend Tristan Thompson.

Khloe has spoken out before about how happy she is that the new generation of the famous family will be able to grow up side by side.

"I am now so excited my daughter will have forever best friends with Chicago and Stormi!!" Khloé tweeted soon after revealing the sex of her baby on the family's E! reality show. "God is great!!! Thank you Lord for our princess."

It also gave Jenner and Khloe the opportunity to experience their first pregnancies together.

"What a magical ride it's been!" the Good American designer wrote in a congratulatory post when Jenner announced the birth of Stormi. "I'll miss you bumping along with me. Never in a million years did I think we would do this together but it's been that much more special because of it. God is so great!! He had His plan all along! I love you little mama, love big mama."

Photo credit: Instagram/Kylie Jenner