Josh Byrne (born on February 15, 1984 in Los Angeles, California) is an American actor best known for his role as Brendan Lambert on the ABC family sitcom Step by Step a role he played for six out of the show's seven seasons, with his one year disappearance being unexplained during the CBS season. His other television credits include Who's The Boss? and The Family Man as well as the feature film Mr. Saturday Night playing the younger version Billy Crystal's character and co-starring with his then-future Step By Step co-star Jason Marsden who also played Crystal's character as a teenager.