The elder sibling by four-and-a-half years, Finneas became his sister’s indispensable collaborator, co-writer and producer, the pair continuing to compose and record together from a bedroom in their Highland Park home even after Eilish’s emergence as a global phenomenon. “Probably 75-80 percent of the songs are written with us sitting next to each other at a piano or with a guitar, singing a melody together,” he told Variety in 2019. “It’s like a relay race — we really feel like we both have to kill our portion of it to get to the finish line.”