Who is Finneas O’Connell, and how did he get five Grammy nominations? (Hint: Billie Eilish stans him)

Billie Eilish’s six Grammy nominations — including nods in all four major categories, the youngest act ever to do so — made history on their own. The 17-year-old is a generational talent who has already reshaped pop music to her image.

But her 22-year-old brother, producer and co-writer Finneas O’Connell, is up for five of those awards alongside her. Though he’s a less visible part of Eilish’s rise, his productions have helped shape her hushed goth-pop sound and bolstered her commitment to radical artistic independence.

Finneas “understands my life and how I work, and that’s all I really need,� Eilish said in a recent interview with The Times. But their chart-topping intuition did take them by surprise. “I thought nobody would like ‘Bad Guy’ when we made it, and I thought nobody would like ‘When the Party’s Over.’ And those are two of my biggest songs, so I don’t know what the [heck] to expect.�

That moxie indeed landed her a No. 1 single in “Bad Guy� and billions upon billions of streams. But Finneas has also released his own solo debut and produced his first No. 1 for another artist as well.

O’Connell, raised in Los Angeles’ Highland Park neighborhood with his sibling, had some success as an actor before his sister’s ascent, starring in the final season of “Glee� and landing a small role on “Modern Family.� But his work with Eilish, starting from “Ocean Eyes� up through her new single “Everything I Wanted,� defined his creative life and made him something like Drake’s producer Noah “40� Shebib for Gen Z — an instrumentalist whose clear and distinct work for one artist remade pop music.

O’Connell’s sound with Eilish is defined by accommodating her whisper-close vocals. He told Rolling Stone, “If you play a lot of instruments in that range, her voice sounds foggy — but things like bass, kick drums, and low, clocky snares can co-exist and not conflict.� It’s a challenging sound for top 40, but the timing was clearly right for something testy and bracing — a whole class of singers like Clairo are following Eilish in melding electronic pop, R&B and emo melancholy.

Finneas plays live with Eilish and has, unsurprisingly, been preoccupied with her large-scale tour around her smash debut LP, “When We All Fall Asleep, Where Do We Go?� Their collaboration will undoubtedly continue as she settles into what should be a long career.

But he’s already asserting his talent in new arenas. He co-produced “Lose You To Love Me,� the recent single for Eilish’s Interscope labelmate Selena Gomez, her first Hot 100 No. 1. That song’s a more traditional piano power ballad, but it shows he has range outside the intimate, jittery sounds he uses with Eilish.

His October solo debut, “Blood Harmony� is a confident, crisply produced work that, while obviously forgoing his sister’s idiosyncratic star power, also makes a strong case for his own vision as a writer and producer.