Michael Hilary Reuel "Mick" Tolkien (October 22, 1920 - February 27, 1984) was the second son of J.R.R. and Edith Tolkien.
When Michael lost his puppet dog on a holiday, his father wrote Roverandom to console him. Michael also owned the puppet on which Tom Bombadil was based.
Michael's grandson is Royd Tolkien, who cameo'ed as a Ranger in Peter Jackson's The Return of the King.