I'm surprised this isn't in The Lost Boys book, and that Barrie didn't even mention it! Bevil Quiller-Couch, or The Pippa as Barrie called him as a small child when Barrie did the first picture book with him and Porthos, died on February 6th 1919 during the Spanish flu pandemic after World War l. Bevil and Barrie were close friends when Bevil was small (before Barrie met the Llewellyn Davies brothers) and Barrie frequently wrote to Arthur Quiller-Couch, Bevil's father, frequently, so I'm very surprised Barrie never mentioned Bevil's death!
2 additional interesting facts:
1. Arthur Quiller-Couch was the inspiration for the character of Ratty in Kenneth Grahame's Wind in the Willows.
2. Bevil was engaged to a woman named
May Wedderburn Cannan, who was the cousin of Gilbert Cannan! Bevil wrote love letters to her while he was in the war, which were compiled into a book called Tears of War published in 2002.