The characters in Cheaper by the Dozen are represented by the parents and children of one large family, the Gilbreths. The work of non-fiction was written by two of the twelve children, Frank Jr., and Ernestine. The family includes the parents, Frank Bunker Gilbreth, Sr. and his wife, Lillian Moller Gilbreth, who ran an engineering firm which specialized in studying and implementing the efficient use of time for industrial concerns. Their study of time efficiency methods spilled over in the everyday lives of the large family. Frank ran his family as if it were one of his experiments with time charts for simple hygiene and dressing activities to see if time could be used more wisely. Frank Jr. readily participated in and extended the experiments. The rest of the children were named Anne, Bill, Lillian, Martha, Jack, Jane, Fred, Mary, Bob, and Dan. Anne was the oldest of the children, while Jane was the youngest. A little known fact is that Mary died when she was only six years old, therefore the much heralded "dozen" children never did exist at one time. The older children were charged with caring for the younger children while Lillian took care of the “intermediate” children and babies.