His stepfather Chamber was accused of rape. This event is considered to be a birth of the first thee Billy's personalities - no name boy, Christene, and Shawn
His later personalities:
1. Billy Milligan (William Stanley Milligan) is the core personality.
2. Arthur is an extremely sophisticated and educated Englishman. An expert in science and medicine, with a focus on hematology. He is in "the spot"—that is, in charge of the shared body—during times that required intellectual thinking. Arthur is one of only two personalities who could classify a person in the group as an undesirable.
3. Ragen Vadascovinich is the "keeper of hate." His name comes from the words "rage again." Ragen describes himself as Yugoslavian, has a Slavic accent and can write and speak in Serbo-Croatian. He controls the spot in dangerous times and can designate group members as "undesirable." He admitted committing robbery in order to support "the family," but had no knowledge of the rapes.
4. Allen is a con man and a manipulator. He is the most common person to talk to the outside world. He plays the drums and paints portraits. Also the only right-handed self. He is the only personality that smokes cigarettes.
5. Tommy is the escape artist; he is often confused with Allen. He plays the tenor sax and is an electronics expert. He is also a painter, specializing in landscapes.
6. Danny is afraid of people, especially men. He only paints still lifes, saying that this was because Chalmer made him dig his own grave and buried him in it.
7. David, age eight, is the "keeper of pain." He comes to the spot to take the pain of the others.
8. Christene, age three, was the one who would stand in the corner in school when "Billy" would get in trouble. She has dyslexia, but Arthur taught her to read and write. Ragen has a special bond with her.
9. Christopher, Christene's brother, plays the harmonica.
10. Adalana, a lesbian, cooks and cleans house for the others, and writes poetry. Milligan's attorney claimed that Adalana had admitted to committing the rapes without the knowledge of Milligan or the other alters.