Talk:Grimm/@comment-193.22.166.88-20170328050449/@comment-25862208-20170328052642

It was in "Bad Teeth" where Kelly told Nick that being a Grimm is something that's inherited, but not everyone inherits the Grimm trait, such as Nick's Uncle George. She added that nobody knows when it's actually going to "hit" them or even if they have inherited the trait. Josh Porter is another example of someone with Grimm heritage who actually wasn't a Grimm.

The Grimm book that chronicles the family history of every Grimm (formerly belonged to Josef Nebojsa) also showed that more than a century can pass before the trait reappears again in some instances, the Nebojsa family history being one example. It seems logical to assume that when two Grimms have children, the likelihood of them being a Grimm increases.