Who is Sid Dorsett from Sybil and what is their importance?

Sid Dorsett is one of Sybil's two male personalities. He derives his name from Sybil's initials, and he identifies strongly with his father, Willard Dorsett. Sid likes to build things, he even builds a partition in Sybil's apartment. He refuses to accept Dr. Wilbur's explanation that he exists within a female body and has no hope of becoming a man. Sid, like Mike, is nonneurotic and is able to control his anger. Sid is an offshoot of the Peggys.