Kenneth Murtaugh is one of the youngest (if not the youngest) son of Jimmy Murtaugh and Sarina Murtaugh. He also gets called Kenny the Maniac during the movie. He is also Mark Baker's friend and is often the one to get the redheaded Baker boy in trouble. Kenneth dives into the lake with his siblings after claiming that they like the Bakers at the Labor Day Cup games.
He crashes a golf cart into the tennis court and knows the map of Lake Winnetka and the woods around it. He, along with Mark, leads the two families to the road. Kenneth winds up waiting at the hospital with everyone else.
Kenneth Murtaugh is played by Alexander Conti in the second film.