Chris Willman Senior Music Writer and Chief Music Critic There aren’t a lot of precedents in pop music for the pairing of Billie Eilish and Finneas, when it comes to brother-and-sister performing or songwriting duos. But in the world of music for films, it might not be too soon to start considering a comparison with a very famous married duo: Alan and Marilyn Bergman, the long-reigning king and queen of movie theme songs.