John is the eldest child of the Grimes family. In The Rockpile, the reader learns that John is not the son of Gabriel Grimes, the patriarch of the family, but a child from a previous relationship Elizabeth Grimes had. It is unclear if John is aware of his illegitimacy, but it is clear that Gabriel is aware of it and it makes him very unhappy. For this reason, John is often the object of his father's anger and abuse.