1. Happy birthday to my favorite cousin sister—here’s to a year as awesome as you are!
2. Another trip around the sun with my ride-or-die cousin? Cheers to the best one yet!
3. To the cousin who feels more like a sister: Happy birthday—love you to the moon and back.
4. Happy birthday! Thanks for being the chaos to my calm (and the snack thief to my stash).
5. Wishing my cousin sister a day as bright, funny, and amazing as she is.
6. Another year older, but still my favorite partner in crime. Happy birthday, cousin!
7. To the girl who’s been there through it all: Happy birthday—here’s to hundreds more memories.
8. Happy birthday to my cousin, my confidant, my sister at heart. You’re the best!
9. Hope your birthday’s full of all the things you love—including me, obviously.
10. Cheers to my cousin sister! May this year be your happiest, boldest, and best.
11. Happy birthday! Grateful every day that you’re more than family—you’re my friend.
12. To the cousin who makes family gatherings 10x better: Happy birthday, love you!
13. Wishing you a birthday as wonderful as the way you make everyone around you feel.
14. Happy birthday to my partner in gossip, laughter, and all things fun. Let’s celebrate!
15. Another year, another chance to be amazing. You’ve got this, cousin sister—happy birthday!
16. To my cousin, my rock, my sister: Happy birthday. Here’s to all the joy ahead.
17. Hope your birthday’s as sweet as the memories we’ve made. Love you tons!
18. Happy birthday! Thanks for being the kind of cousin who feels like forever.
19. To the best cousin sister ever: May today be full of cake, smiles, and zero adulting.
20. Happy birthday—you’re not just family. You’re my favorite person. Let’s make it count!