Raymond is mentally challenged, with a mental age much lower than his chronological age.
Squeaky (Hazel Elizabeth Deborah Parker) does not say exactly what is wrong with her brother, but she tells us that “he needs looking after cause he’s not quite right.” She does say that he has a big head, and her job is to look after him.
Raymond has a big imagination, but little inhibition.
[He’s] subject to fits of fantasy and starts thinking he’s a circus performer and that the curb is a tightrope strung high in the air.
She also says that he might dash into traffic trying to save pigeons. Basically, he acts like a young child instead of an older one that knows better.
Squeaky also protects her brother from kids who insult him, tease him, or bully him. They tease him because he can’t defend himself, and because his head is large.
Although she sometimes gets tired of always looking out for him, Squeaky respects and cares about her brother. She wants him to be happy, and does her best to protect him. She lets him be who he is, because to her it is important to be who she is.