Billie Eilish seen officiating brother Finneas O'Connell's wedding in photos from Montecito ceremony

MONTECITO, CALIFORNIA: Billie Eilish made sure to be by her brother Finneas O’Connell’s side on his special day.

O’Connell tied the knot with his girlfriend Claudia Sulewski in an intimate ceremony at the San Ysidro Ranch in Montecito, California, on Saturday, August 29, after nearly eight years of dating. Eilish also appeared to have a special role in the ceremony, as she seemingly officiated the wedding.

Billie Eilish officiates brother Finneas O'Connell’s wedding as she turns heads in plunging gown

Eilish’s photos from her brother's wedding quickly spread across social media, with the singer seen posing alongside her brother and his bride. 

She turned heads in a plunging, olive-green corset gown with an off-the-shoulder neckline and an elegant satin skirt. Eilish opted for minimal makeup, keeping the focus on her stunning dress.

She kept the rest of her look simple but elegant, wearing her shoulder-length auburn bob in a sleek side part. Eilish completed the outfit with diamond drop earrings and dark lipstick, adding a bold touch to her wedding guest look.

The 'Happier Than Ever' singer also attended the reception with her boyfriend, Nat Wolff.

As for the bride, Sulewski looked stunning in a sleeveless Oscar de la Renta ballgown with a flowing skirt and matching bridal scarf. She completed her wedding look with a sheer, floor-length veil and white peep-toe heels, as per Vogue.

Finneas O'Connell and Claudia Sulewski’s wedding guest list

O’Connell and Sulewski’s wedding brought together a star-studded guest list. Celebrities like Justin and Hailey Bieber, Jason Sudeikis, Kristen Bell, Dard, Emma Chamberlain, Rachel Sennott, Nina Dobrev, Rebecca Black, Devon Lee Stassie Karanikolaou, and Jesse Jo Stark attended the weekend wedding, as per Archyde.

O’Connell’s parents, Maggie Baird and Patrick O’Connell, were present to watch their son exchange vows. Their dogs, Peaches and Moose, also joined the celebration, adding an extra personal touch to the couple’s special day.

For those unaware, O’Connell and Sulewski’s love story began in 2018 when they met on a dating app. After years together, the couple announced their engagement on September 24, 2025, with a joint Instagram post captioned, “Forever and ever 9.22.”

O’Connell even wrote several songs inspired by Sulewski, including the 2019 track 'Claudia', while Sulewski directed and starred in the music video for his 2022 song 'Mona Lisa, Mona Lisa'.