Billie Eilish, 21, kisses boyfriend Jesse Rutherford, 31, at her star-studded birthday party in LA

Billie Eilish Celebrates 21st Birthday With Star-Studded Christmas Themed Bash

Kendall Jenner and Hailey Bieber in photo booth at Billie Eilish's star-studded 21st Birthday

Billie Eilish Celebrates 21st Birthday With Boyfriend Jesse Rutherford & Star-Filled Party - Celeb Guest List Revealed!