Grandpa "Bampy" Jefferson is Rowley's Grandfather and Robert Jefferson and Rowley’s Uncle’s father. He made a cameo appearance in Rodrick Rules in which Rowley's family celebrated his birthday and Greg was invited to. He is unhappy with the flavour of the cake and says that he wants chocolate cake for his next year's birthday, but Greg says that it would only be possible if he is alive the next year. This angers Rowley's father.
In Diary of an Awesome Friendly Kid, Rowley mentions he has an old log cabin (which is now owned by his dad) and calls his grandpa by Bampy, since he couldn't say grandpa. Bampy was also the only thing he could really say before his death.
Grandpa is shown with a long nose, a few strands of hair and a few wrinkles.
Grandpa is shown with glasses, a beard and a granddad hairstyle.
- Diary of a Wimpy Kid Online (First appearence)
- Diary of a Wimpy Kid: Rodrick Rules (First book appearance)
- Diary of an Awesome Friendly Kid: Rowley Jefferson's Journal
- Diary of Greg Heffley's Best Friend