Billie Eilish broke through in 2019 with her album "When We All Fall Asleep, Where Do We Go?" The album contained the hit single "Bad Guy" and Eilish soon became one of the most successful artists in recent memory.

She co-wrote and co-produced the album with her brother Finneas O'Connell. The two swept at the 2020 Grammy Awards, cementing their place in the music business. Finneas' success has extended to producing and writing for other artists. He's also developed a successful solo career with his own music.

However, before Eilish stepped into the music industry, Finneas started an acting career that led him to the hit series Glee.

Finneas Reflects On His Grammy Wins With Sister Billie Eilish In 2020

Finneas' sister Billie Eilish received mainstream recognition in 2019 with her album "When We All Fall Asleep, Where Do We Go?" Finneas co-wrote and co-produced the album with Eilish. The two received a ton of nominations at the 2020 Grammy Awards.

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The two swept at the ceremony, with Finneas telling Fader that he was surprised by the wins.

"I was hopeful that we’d even get one, and never thought we’d get the sweep we did — ridiculous," Finneas said.

Related: 10 Pics That Prove Billie Eilish And Finneas Are Sibling Goals

He continued, "We were performing, so I wanted to be top of our game when we were on stage. If you’re guaranteed something you can prep your speech or whatever. You won’t know until 30 seconds before you’re making a speech if you have to make a speech so it’s hard to prepare anything good."

Finneas Releases His Debut Solo Album 'Optimist' In 2021

While co-writing and co-producing songs with Eilish, Finneas released a lot of solo material. His debut EP "Blood Harmony" was a huge success and got fans excited about his first full album. Their prayers would be answered when he dropped his debut studio album "Optimist" in October 2021.

When speaking to Alternative Press, Finneas explained what he hoped to accomplish with his first album.

"My favorite albums are cohesive bodies of work, and I wanted this one to be the same way," Finneas said. "As a producer for other artists, it can be easy to make a song that sounds like this or a song that sounds like that, but I wanted this to feel like one artist. That was my biggest challenge, making sure that I have a real identity on this record."

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Finneas explained that the songs on "Optimist" reflect his own perspective on life. He wanted to take the listeners on a personal journey in a completely honest way.

"The through line would be some version of honesty and transparency," he said. "These songs are really how I feel about my life and the world. There’s metaphor on this album, but there’s nothing that didn’t stem from my life experience or something that I think about constantly. So hopefully it’s a road map to getting to know me better and getting to know what keeps me up at night."

Related: Billie Eilish’s Brother, Finneas, Releases Deluxe Version of ‘Blood Harmony’

The album was favorably received by critics and Finneas released a deluxe version in 2022. It included acoustic versions of some of the album's tracks, recorded live at Abbey Road Studios. Finneas also recorded a cover of The Beatles song "The Fool on the Hill."

Finneas Played Alistair On The Television Series 'Glee' In 2015

Before his enormous success in the music world, Finneas got bit by the acting bug. He first appeared in the film Bad Teacher in 2011 and worked alongside his mother in 2013's Life Inside Out. He even had recurring guest roles on the shows Modern Family and Aquarius.

However, the most memorable of these early roles was his role in the sixth and final season of Glee. Finneas played Alistair, the dreamy, long-haired love interest of glee club member Spencer.

Finneas reflected on his audition process when speaking to GlambergirlBlog in 2015.

"The first audition I ever did for Glee was in 2013," he said. "I got asked to audition but it was really me putting a camera on myself in the kitchen and doing a self tape and that’s pretty common of you doing an audition at home then they’ll want to see you. Then I went back a couple of months later for a different role and I did the preliminary audition which was just singing, then I went back a few weeks later for an audition for like Ryan and stuff. I didn’t get that role."

Finneas was asked to return for several other auditions and finally landed a part on his fifth try.

"I went in and said my stuff, did the part and like a day later, because of the nature the way things were so fast in the last season, it was such a fast process once I was cast," he explained. "They called me the next night and told me I got the job. The next day I had wardrobe and the next day I started. It was such a crazy week."

Related: How Much Is Finneas O'Connell Worth?

At the time, Finneas was fronting the pop rock band The Slightlys. He told All Access Music how his experience on Glee helped him become a better performer.

"You always have to give it your all on that show and I just thought to myself, 'Then I should always give it my all whenever I perform.' Sometimes it’s hard to remember to do that live because you’re juggling so many things between playing and singing and working the crowd and communicating with the other guys in the band, but you have to remember that the most important thing is to put on a great show."