Billie Eilish officiated her brother Finneas’ star-studded wedding to Claudia Sulewski on Saturday. The “Birds of a Feather” singer, 24, wore an olive-green dress as she stood between the bride and groom at San Ysidro Ranch in Santa Barbara, California, per photos obtained by Page Six. At one point, she was seen wiping at her eyes while her brother read his vows, before laughing wholeheartedly. For their special day, Finneas wore a classic black suit, while Sulewski stunned in an Oscar de la Renta dress. During the outdoor ceremony, the couple said their “I do’s” in front of Justin and Hailey Bieber, Dax Shepard and Kristen Bell, Nina…