book Cheaper by the Dozen written by Frank B. Gilbreth, Jr. and Ernestine Gilbreth Carey was the life story of the Gilbreth family before Mr. Gilbreth died. Frank Gilbreth, Jr. and Ernestine Gilbreth were two of the twelve children. Mr. and Mrs. Gilbreth, both industrial engineers, ran a firm, Gilbreth, Inc. which was employed as "efficiency experts" by major industrial plants in the United States, Britain, and Germany. Mr. and Mrs. Gilbreth had twelve children, six girls and six boys.