Sinbad - Paddy’s brother - is known as Francis to his parents.
Sinbad is a sensitive child, and the other boys see this as a weakness. Paddy first introduces us to the character in the opening section by saying “Sinbad, my little brother, started crying.”
This is followed by Paddy having to wait for Sinbad when the boys are being chased. Therefore our first impressions of Sinbad are of a child who is easily annoyed and cannot keep up with the rest of the gang.
We learn from Paddy that Sinbad never smiles in childhood photos, "I hated him … He cried. He wet the bed. He got away with not eating his dinner. He had to wear specs with one black lens.”
Sinbad’s status as younger brother makes Paddy see him as childish and weak.
The fact that Sinbad seems placid and goes back to playing with Paddy and his friends after they are so cruel to him shows how he endures all the torment without complaining.
Poor Sinbad becomes just as aware of his parents’ problems as Paddy as the novel progresses. We see him trying to defuse the situation by laughing at one stage.
During a particularly loud fight, Paddy asks Sinbad “Did you hear that?” But Sinbad ignores him. Paddy wonders whether “Maybe he could decide to hear and not hear things.”
Perhaps this is Doyle suggesting that Sinbad’s sensitivity meant the only way he could cope was by being selective about what he actually acknowledged, thereby remaining in denial about the severity of the situation.
The boys are very competitive and jostle for their position in the gang. Sometimes Paddy and the other boys try to show their dominance by picking on Sinbad, which often creates sympathy for this character.
The scene where Paddy burns Sinbad is shocking and Paddy’s vivid description of how “He squirmed but I held onto him” and “I just wanted to hurt him” highlights the cruelty and intent of those who were torturing him. Sinbad is permanently scarred.
Sometimes even Paddy shows sympathy for his brother, and consequently he attempts being protective or kind towards Sinbad.
He refuses to carry out Mr Hennessey’s orders when he tells Paddy to show their mother Sinbad’s ruined exercise book.
Later in the novel - as they seem to become closer in response to their parents’ constant fighting - Paddy asks his brother whether he wants to be called Sinbad or Francis.
Later on - as Paddy realises that his friends don’t really care about him - he says “I realised something funny; I wanted to be with Sinbad.”
Sinbad is the only one who really knows what Paddy is going through at home, and as he grows up Paddy becomes more sympathetic to and more appreciative of him.