Parents:
* Frank Gilbreth (father)
* Lillian Gilbreth (mother)
Children:
* Anne Gilbreth (oldest daughter)
* Margaret Gilbreth (second oldest daughter)
* Ernestine Gilbreth (third oldest daughter)
* Frank Gilbreth Jr. (oldest son)
* William Gilbreth (second oldest son)
* John Gilbreth (third oldest son)
* Mary Gilbreth (fourth oldest daughter)
* Daniel Gilbreth (fourth oldest son)
* Elizabeth Gilbreth (fifth oldest daughter)
* Joseph Gilbreth (fifth oldest son)
* Martha Gilbreth (sixth oldest daughter)
* Thomas Gilbreth (sixth oldest son)
Other Notable Characters:
* Mrs. Hartigan (the family's housekeeper)
* "Big Bill" McFee (a family friend and neighbor)
It's worth noting that the children are often referred to by their nicknames:
* Anne: "Annie"
* Margaret: "Maggie"
* Ernestine: "Ernie"
* Frank Jr.: "Frankie"
* William: "Billy"
* John: "Jack"
* Mary: "Molly"
* Daniel: "Danny"
* Elizabeth: "Libby"
* Joseph: "Joe"
* Martha: "Marty"
* Thomas: "Tommy"
I hope this list helps! Let me know if you have any other questions.