The current issue of WIPO Magazine features a story about a boy who may be the world's youngest patent holder. Samuel Thomas Houghton of Buxton, UK was only three years old when he had an idea for an improved broom. His father, a patent attorney, applied for a GB patent, which was granted on April 2, 2008 (GB2438091).
It's impossible to know for sure if little Sammy is the world's youngest inventor since the inventor's age is not usually stated in patent applications. But I can think of at least one other very young patent holder from Minnesota. Steven Olson of St. Paul, MN, also the son of a patent attorney, was granted a patent in 2002 for a new "method of swinging on a swing" (US6368227). I believe that little Stevie was only 4 or 5 when his father applied for his patent. His patent is often cited by critics of the USPTO as an example of a low quality patent that should never have been issued. It does look like a vanity project, given that it's hard to imagine how one would go about commercializing such an invention. I guess it's no surprise that he let it expire in 2006.
I'm the librarian for research services in the Engineering and Science Library at Queen's University in Kingston, Ontario. I've been working with patent information since 1991, including seven years at the U.S. Patent and Trademark Office. I believe that the dissemination of patent information is a public good and should be promoted, especially in the education of science and engineering students.