Billie Eilish and her brother Finneas O'Connell make music together. Wikipedia describes Finneas as a singer, songwriter, musician and producer who has written and produced for his sister and is credited on all of her projects (Wikipedia). That makes this a creative partnership, and this article reads their charts that way, not as a romance and not as a compatibility score.
What they've said about working together
In a 2024 NPR interview with Leila Fadel and Phil Harrell, the siblings talked about how they work (NPR). In brief:
- Finneas described production as a way of telling a song's story and sentiment, and said their communication got better with practice.
- Billie described being able to disagree honestly, without having to perform niceness, and spoke about her own bravery as a singer and about having permission not to release her most vulnerable writing.
- They described reworking the song "Blue": they liked its second half but not its first, and layered drums changed how it felt.
That's their own account. What follows is a symbolic reading of two birth dates, and it doesn't explain any of it.
The birth inputs, and what's uncertain
- Billie Eilish: born December 18, 2001, in Los Angeles (Wikipedia).
- Finneas O'Connell: born July 30, 1997, in Los Angeles (Wikipedia).
Neither Wikipedia article gives a birth time. Our catalogue stores a time for Billie, but we couldn't corroborate it from a source we read, so this comparison doesn't use it. Both charts are date-only: each Los Angeles birthday was sampled 25 times in local time, every hour plus 23:59, with Lunara's Swiss Ephemeris engine. That means no Rising sign, no houses and no Moon degrees. The ranges below are sampled envelopes, not proof for every minute.
Across the whole day:
- Billie: Sun about 26½–27½° Sagittarius, Mercury about 4–5½° Capricorn, Venus about 20–21° Sagittarius, Mars about 7° Pisces, Moon in Aquarius all day.
- Finneas: Sun about 7–8° Leo, Mercury about 4–5° Virgo, Venus about 8–9° Virgo, Mars about 21° Libra. His Moon moved from Gemini into Cancer at about 5:37 p.m. local time, so it's Gemini or Cancer.
The centrepiece: two Mercurys, one trine
Here's the contact that stands out. Billie's Mercury sits at about 4–5½° Capricorn. Finneas's Mercury sits at about 4–5° Virgo. That's 120° apart, a trine, and it stays within 0–1.6° across all 625 pairings of the two days' samples. Our orb convention allows 6° for a trine, so this one is well inside.
Mercury is the planet astrologers connect with language, ideas and craft. Both Mercurys are in earth signs, the element traditionally linked with practicality, patience and making things that hold up. Capricorn is read as structure and long-range shaping; Virgo as precision and refinement. A trine between them is read as an easy flow: two ways of thinking that tend to understand each other's method without much translation.
That's a description of how two placements meet. It isn't evidence of trust, a measure of conflict, or the reason their work sounds the way it does.
Natal charts versus a two-person comparison
It helps to keep two things apart.
A natal chart is one person's sky. Finneas's Mercury and Venus together in Virgo, or Billie's Moon in Aquarius, belong to each of them alone, and their profiles read those on their own terms.
A two-person comparison, called synastry, only exists when you set the charts side by side. The Mercury trine above isn't in either chart separately. Two more contacts also hold across every sampled pairing: Billie's Venus sextile Finneas's Mars (orb 0–1.6°), and Billie's Mars opposite Finneas's Venus (orb about ½–2½°). In astrology those are read as easy cooperation and as a productive push-and-pull. They're symbols for a conversation, not a forecast.
A prompt for your own creative partner
If you make things with someone, a co-writer, a bandmate, a design partner, try this together:
- "When we disagree about a draft, what does each of us actually want the piece to say?"
Say your answers separately first, then compare. The "Blue" story is a good model: liking one half of something and not the other is useful information, not a failure.
Compare your own charts
To see how your chart meets a collaborator's, the synastry chart lets you enter both people's birth dates and places, with times if you know them, and shows the contacts between your charts. You can also browse more musicians' chart readings on our celebrities page, or open the full profiles for Billie Eilish and Finneas O'Connell.
If you'd like to see how a written natal reading handles placements like these, start with the sample natal reading. If you want your own, there's an optional paid personal birth chart reading. It's an automated, written interpretation of your own chart, not a reading made for these siblings, and not a measure of creative ability. What's included and the price are shown before you buy.
Text written with AI assistance. The positions are calculated, not estimated.