What is the importance of the Spring family in the novel, The Face on the Milk Carton?

Jennie Spring is the missing girl on the milk carton. When Janie goes to New Jersey, she sees three red-headed boys walk into the Spring house and assumes that they are her brothers. Janie also has a memory of twins that could be other members of the family. There is also a dog named Honey. A voice presumed to be that of Mrs. Spring appears toward the end of the novel, but otherwise the Spring family does not appear in the context of the story. However, Mr. and Mrs. Jonathon Avery Spring still play prominent roles, as Janie continues to remember bits and pieces of her life with them before she was kidnapped.