Sigmund Freud
Freud was a neurologist who founded the practice of psychoanalysis. Throughout his book, Eriskon references Freud either to back up his points or to disagree with him. Freud proffered many theories about childhood development, his primary concern being the sexual relationships between parents and children which have a prominent impact on adult psychology of the children after they're grown. While Erikson agrees with Freud on many points, he does not credit sexual development as strongly as his predecessor. Erikson prefers to think in terms of ego.
Anna Freud
Freud's daughter, Anna, who belongs to his profession as well helped Erikson develop his eight stages of childhood development. Placing great stock in Freud, Erikson turned to his daughter for guidance when hashing out his theories.
Joan Erikson
Her contribution to her husband's book is regarding the life stages. She adds another stage, the ninth which she calls the "Pyschosocial Crisis." In her early 90s, Joan demonstrated why she believed that the ninth stage was a necessary addition to her husband's work. Faced with the unique challenges of old age, she realized that all of the previous eight stages were being repeated in her life but backwards.