Billie Eilish's older brother Finneas' 20th birthday post to Billie is so sweet.

Finneas Posted The Most Supportive, Loving Note For Billie's Birthday

"I’ll be your #1 fan till the day that I die."

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Billie Eilish just turned 20 and various celebrities like Beyoncé and Billy Porter have wished the singer a very happy birthday. Still, there’s one birthday post that can’t go unnoticed: Eilish’s brother Finneas. The Happier Than Ever singer and her brother are notorious for being musical partners in addition to siblings. So, when it came to celebrating his little sister’s big day, Finneas’ Instagram post for Billie Eilish’s 20th birthday was so sweet and did not disappoint.

The 24-year-old wrote an endearing message along with some silly pics of his little sister where he said he’ll always be Billie’s number one fan. “20!!!!!!!!! Watching you grow and become the thoughtful, incredibly kind, talented, hilarious and hardworking person that you are today has been the joy of my life! I’ll be your #1 fan till the day that I die. There is truly nothing I love more than being your big brother. Happy birthday!!!”

Along with the super supportive note, Finneas shared a couple of snaps of his sis chilling in a green windbreaker, and celebrated her silly side by posting a video of Billie playfully biting their mother’s hair.

Finneas was not the only member of the Eilish family to wish the “Bad Guy” singer a happy birthday. Billie’s mom Maggie May Baird also posted loving words on Instagram that were accompanied by a slideshow of pictures of Billie when she was younger. “Happy Birthday Billie Eilish Pirate Baird O'Connell! You are funny, and complicated, and goofy, and tough, and strong, and brilliant! Your joy for the holidays and all things birthday and Christmas, gifts so much joy to our family. How can someone be so powerful and so goofy and childlike at the same time? I don't know, but you make life more exciting and tender. I love you with ALL my heart and soul.”

Earlier in December, the musical siblings performed on Saturday Night Live, where they played their recent collaborations “Happier Than Ever” and “Male Fantasy” in Studio 8H. Finneas also made an appearance in one of the sketch’s that night as well where he played a chaotic hotel employee.

Finneas and Billie first appeared on SNL as musical guests in 2019, and Billie had some heartfelt words for her older brother. “MY BROTHER IS MY BESTFRIEND AND WE DID SNL LAST NIGHT AND IT WAS A PEAK LIFE EXPERIENCE. WOW. THANK YOU LIFE FOR GIVING ME WHAT I HAVE.”

Billie and Finneas have often been photographed together attending award shows, walking the red carpet, and have even accepted awards together. Finneas has always been super proud to work with his little sister, and while accepting their 2021 Grammy for Best Song Written for Visual Media, he ended their speech and said, “Thanks, Billie, for letting me write the song with you. I feel very lucky to be your brother.”

It’s clear the two siblings love working together and it seems like they’ll always be each other’s number one fan.