Frank's brother Malachy, a year younger, is a beautiful child, with "blue eyes like...mother...golden hair and pink cheeks". Frank, in contrast, looks more like their father, with "black hair and...cheeks...white in the mirror". Malachy is more easy-going than the introspective Frank. When the boys are young, people say that "Malachy is the happiest child in the world", while "Frankie has the odd manner like his father". Women automatically smile when they see little Malachy, and Frank wonders why they don't react to him in the same way (Ch.I).
Frank and Malachy are both imaginative and creative, and shouldered with responsibility at a young age. Frank, by virtue of being older and having a more analytical nature, appears to be more reliable. When they are sent by their mother to find their wayward father and bring him home from the pub, it is Frank who directs the search while Malachy takes on the task of delivering the dramatic speech to his father about how the money he is spending is for the babies who are hungry.
Malachy is more robust than Frank, and by the time they reach their preteen years, he is bigger than his older brother, who has been sick with typhoid. Frank is embarassed when he is put in Malachy's class, because although he is no longer bigger, he is still older (Ch.VIII).