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John Heffley is the cousin of Frank Heffley and uncle to his children who appeared only in The Ugly Truth. John used to be part of The Bachelors, but he got married during Spring time around Greg's seventh grade. Greg believes that he may have gotten married just so he wouldn't have to sleep in the room with the rest of the Bachelor members.
- Loretta Heffley is probably his mother.
- Diary of a Wimpy Kid: The Ugly Truth (First and only appearance)