The top mistakes in Cheaper by the Dozen (1950) http://www.moviemistakes.com/film4150 en Sat, 17 Dec 2005 06:55:40 +0000 57706 The movie shows the last Gilbreth child born as a boy, Robert. The last child was actually Jane. 56260 All twelve children were never alive at one time. Mary, along with some of her siblings, came down with diphtheria, in 1912. While the others recovered, Mary died on January 31st. The family continued to refer to the Dozen, even though all twelve were never contemporaries. The book refers to them as a dozen, and the movie & stage play portrays all 12 at a time.