I have this headcanon about Bill Belfry being the only one who knows about Bertie's romantic interested in Jeeves. Bill is secretly bisexual himself but decided to only ever follow the safe path. He once had a crush on Bertie and is still very fond of him. Bill never tried to become one of Bertie's closer friends, is content with admiring him from afar but he cares about Bertie like none of Bertie's other friends and pays close attention to him. That's why things are obvious to Bill whenever he hears Bertie talking about Jeeves. After getting to know Jeeves, Bill hopes for Jeeves to notice and return Bertie's feelings.