Thread:IndigoPengi/@comment-4220590-20180605190849/@comment-4166811-20180806223722

For reference, here's the Sonic Adventure: Navigation Guide's page on them: https://imgur.com/a/zAgZ1

Still just Birdie. It does, however, confirm the relationship between the three of them, saying that Birdie is one of 3 siblings (兄弟 - kyoudai).