On his 26th birthday, Billie Eilish is expressing her affection for her older brother Finneas!

The 21-year-old, seven-time Grammy winner, shared a vintage photo of the couple on Instagram on Monday, showing Finneas ogle her like a newborn.

“Forever, my closest friend. The 21-year-old Eilish captioned the photo, saying, “will never love anyone as much as i love you @finneas happy birthday you are the best thing i have.”

Eilish has made no secret of the importance of her elder brother to her music. In addition to winning numerous Grammy Awards and an Academy Award, the siblings have jointly published two No. 1 albums (When We All Fall Asleep, Where Do We Go? in 2019 and Happier Than Ever in 2021).

Back in July, Eilish disclosed that prior to her and Finneas’ contribution to the Barbie soundtrack, “What I Was Made For?”, they were experiencing a phase of self-doubt that extended well beyond writer’s block.

The day after Eilish’s self-directed music video for the song was released, she spoke with Zane Lowe of Apple Music 1 about how the song came about only when Finneas figured out how to solve their “frustration in writing.”

It is always been Finneas who says, ‘No, no, no, let us write. Now let us write. And to be really honest, we went through a phase where we were both really uninspired, especially during this past winter, Eilish said. “And we have continued to work and produce content. To be honest, we had not composed a song in a minute before that one.”

Finneas also talked candidly about their life in the spotlight earlier this month in an exclusive Song Stories podcast conversation with PEOPLE on iHeartRadio.

He said, “Billie gets to play these arenas and whatever, but her day-to-day life is more challenging than mine,” to Jordan Runtagh, the host. “My unrestrained liberty to stroll down the street, enter a grocery store, sit in a coffee shop, and do whatever else. It is not a challenge when a child approaches me that day and says, “Hey, I love you,” or something similar.”

Finneas went on to say that he would “avoid it” if he could and that he has no desire to become as well-known and well-recognized as his sister.

He did, however, concede that in order for his music to reach as many people as possible, a certain amount of recognition is necessary.

“I should note that I take pride in my music. I would like to spread the word about it. I want as many people to hear it as possible. And I am ready to accept that if it means that I become more well-known,” he declares. “I believe that many individuals aspire to fame, but I do not want to become even more well-known than I already am. It appears to be a major drag.”