Billie Eilish Performs with Brother Finneas at iHeartRadio Music Festival 2021 Night 2!

Billie Eilish and Finneas are rocking out on stage!

The 19-year-old entertainer and the 24-year-old singer/songwriter/producer performed together during Night 2 of the 2021 iHeartRadio Music Festival on Saturday night (September 18) at the T-Mobile Arena in Las Vegas, Nevada.

PHOTOS: Check out the latest pics of Billie Eilish

Other stars making appearances at the music festival included country singer Sam Hunt, Ryan Seacrest, Saweetie, The Kid LAROI, Yungblud, Bachelorette couple Tayshia Adams and Zac Clark, 24kGoldn, and Lil Baby.

In a recent interview, Billie explained the issue she has with the words “fans.” Here’s what she shared…

Make sure to see Billie Eilish‘s stunning red carpet appearance at the 2021 Met Gala earlier this week!

Click through the gallery for 40+ pictures of the stars at the music festival…