Shōnen is a demographic term for manga and anime aimed mainly at early to late teen boys -- basically, between ages 12 and 18. They tend to be Fighting Series focused more on action than relationships, with romance generally either perfunctory or Played for Laughs. Some battles can be sublimated into a form such as a sports competition or even a Tabletop Game.
These are not like that.
Quite often, a series will be published in a Shōnen magazine that doesn't meet these parameters. Whether it's about a forbidden love-triangle, a psychotic mastermind with a god complex, a slice of life about elementary schoolers, a cast full of pretty boys, or just about the most bloody and misanthropic violence you've ever laid eyes on, these series managed to get published in magazines aimed at the wrong audience. But as anyone will tell you, sometimes you have to think outside the box in order to make something great, and these series tried (and I many cases succeeded) to do just that.