At the start of the musical, working class woman Mrs. Johnstone learns she is pregnant with twins and confides in her employer Mrs. Lyons about her fears that she will not be able to support both children. Mrs. Lyons, a wealthy and deceitful woman unable to have children herself, persuades Mrs. Johnstone to give up one of her boys with the promise that she will raise him in the lap of luxury. But when Mrs. Lyons fires the mother in hopes of making Eddie all her own, she is unable to separate herself and Eddie from the Johnstone family or from the lies of the past, leading both families towards a tragic end.
The story is told through the narrator, who is presented as an especially pivotal character, a manifestation of one of the visible themes in Blood Brothers - the idea that life is a game. He treats the characters as players of his game, manipulating their lives and playing off their superstitious beliefs. The narrator is always visible on stage, acting as a Mephistophelean puppeteer of sorts who manipulates the lives and families of Mrs. Johnstone and Mrs. Lyons.
Blood Brothers also explores class differences and the gap between classes through the way both the sons and mothers choose to live their lives. Mrs. Johnstone and Mrs. Lyons are in two very different classes, yet they are unable to avoid each other because of the connection their sons share. The differences in lifestyle, values, and morals of the two families are stark yet subtly done.
The most prevalent theme is within the constant reference to Marilyn Monroe. In the opening song "Marilyn Monroe", Mrs. Johnstone tells of her carefree youth, comparing every aspect of her life to that of the blond bombshell. The song is reprised several...