You've probably seen the name floating around. Usually, it's a typo. Sometimes, it's a meme. But if you’re asking who is William Eilish, the answer is actually more of a family history lesson than a "new celebrity" reveal.
Let's be real: most people are just trying to find Billie Eilish. They might have heard a rumor or seen a weirdly phrased headline and figured she had a twin brother named William or something. Truth is, there is no famous singer named William Eilish. But the name William is actually woven into the very fabric of Billie’s life.
The Real Story Behind the Name
Billie Eilish Pirate Baird O'Connell. That's her full legal name. Notice the lack of "William"?
However, Billie was named after her maternal grandfather, William Baird. He passed away shortly before she was born. In a world of stage names and calculated branding, her parents—Maggie Baird and Patrick O'Connell—wanted to keep that family connection alive.
Honestly, it’s kinda sweet. Her family actually called her "Billie" as a tribute to William. Billie herself has joked about this in old interviews, saying that for the first few years of her life, her family basically treated her like a "William" because they were so attached to the memory of her grandfather.
Why You Keep Seeing "William Eyelash"
If you're deep in the fandom, you know the "William Eyelash" joke.
This whole thing started because of The Office. Billie is arguably the biggest fan of the show on the planet. Rainn Wilson (who played Dwight Schrute) once did a bit where he purposely butchered her name. He called her William Eyelash.
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- It became an instant meme.
- Fans started using it ironically.
- Search engines started getting confused.
Because so many people search for the meme name, "William Eilish" started popping up as a suggested search. It's the classic internet game of telephone. One person makes a joke, ten people misspell it, and a hundred people end up on Google wondering if there's a secret O'Connell brother hidden in a basement somewhere.
Is There a Real William in the Family?
Technically, yes. If we look at her paternal side, the O’Connell tree is full of Williams.
Her great-grandfather was William H. O'Connell. He was an Irishman from County Cork who ran a place called the Clubhouse Bar in Lisbealad. He moved to Boston in the early 1900s. If you’re looking for a "William O'Connell" (which would be Billie's "real" last name if she didn't use her middle name Eilish as a surname), he's the one.
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Finneas vs. William
Sometimes people get Finneas O'Connell mixed up and think his name is William.
It’s not. Finneas is her only sibling. They are famously close, writing almost all their music together in their childhood bedrooms. While Finneas has his own solo career and has produced for everyone from Justin Bieber to Nat Wolff (who Billie is currently dating in 2026), he has never gone by William.
What You Should Actually Know About the Eilish Brand
Since it’s 2026, the "Eilish" name has become more of a corporate entity than just a person. When people search for who is William Eilish, they are often bumping into the massive expansion of her brand.
- The Fragrance Line: Eilish No. 1, 2, and 3 are everywhere.
- The Activism: She recently donated $11.5 million from her Hit Me Hard and Soft tour to climate justice.
- The Transformation: She’s been vocal about becoming a "gym rat" lately, moving away from the baggy clothes that defined her early years (though she still rocks the oversized look when she wants to).
Clearing Up the Confusion
If you see a credit for "William Eilish" on a song, check the source. It is almost certainly a metadata error or a fan-made upload.
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In the music industry, "Eilish" is technically her middle name. Her brother uses "O'Connell." This discrepancy leads people to think there are other family members using different combinations of the names. There aren't. It’s just Billie, Finneas, and their parents.
Actionable Next Steps
If you’re trying to track down a specific "William Eilish" and none of this family history fits, you’re likely looking for a different person entirely or a very specific parody.
To get the most accurate info on the Eilish/O'Connell family:
- Check the official credits on Spotify or Apple Music for song authorship; you’ll see "Billie Eilish O'Connell" and "Finneas O'Connell."
- Follow her mother, Maggie Baird, on social media. She is the unofficial historian of the family and often shares photos of the "real" William (Billie’s grandfather).
- Look into the Irish Genealogy projects centered around County Cork if you're interested in the O'Connell ancestry.
The "William" mystery is really just a mix of family tribute and internet humor. Stick to the official O'Connell/Baird sources, and you'll avoid the rabbit hole of typos and memes.