Actor Mark Harmon is known to most as Leroy Jethro Gibbs from the hugely successful TV show NCIS. But did you know that the actor comes from a very famous family? Mark’s dad, for instance, was none other than former NFL star and broadcaster Tom Harmon. And in February 2019 the star spoke to People magazine about some profound – and slightly profane – advice that his father had imparted to him. Yet while the anecdote may sound like an NCIS scene between Gibbs and Jackson, it’s totally real – and something that Mark has carried with him throughout his whole life.