Robert Jefferson

Robert Jefferson is father of Rowley Jefferson and the husband of Mrs. Jefferson. He is one of the wealthiest people in Greg's neighborhood, as well as the least respected in his neighborhood. In the movie, he is played by Alf Humphreys. He doesn't like Greg because one time Greg and Rowley made a secret language, but Robert cracked the code.

Personality
Robert is fussy, paranoid, temperamental, stiff, shallow and emotional, yet unlike Frank, he usually shows none of these qualities to his son.

He won't let Rowley play any video games with the slightest bit of violence or fighting in it, as he sees them as things that could change Rowley into a different person. He is extremely rude and cannot accept criticism from people he dislikes, as seen in Diary of a Wimpy Kid: Dog Days. In the events of Dog Days, it is shown that he can simply restrict people he dislikes from ever entering his country club again if they dare give any type of criticism about him or his property.

Appearance
Greg depicts Mr. Jefferson with afro-style hair, black shirt, and long pants. There has been an illustration of him in pyjamas, but this was only shown in Dog Days.

Rowley Jefferson
Overall, Rowley and Robert have a close relationship, but this is not shown very clearly until the fourth book, where they share many common hobbies such as tennis. Robert is very protective of his son and won't let anything harm or influence him in any way, which is why Robert does not like Greg very much.

Greg Heffley
Greg and Robert have a very complicated relationship. Although Greg is the best friend of his son, he sees Greg as a terrible influence to Rowley's timid behavior, and does not like the fact that Greg manipulates Rowley to do whatever he wants at Rowley's expense. Robert is very cautious when he lets Greg use his equipment, because like the relationship between Frank Heffley and Rowley, he thinks Greg will ruin his property, such as the Country Club. He sees Greg as a bad influence for several reasons. Examples include Greg's haunted house scam in Diary of a Wimpy Kid, insulting him by stating that he smells like a woman at dinner while trying a "secret language" during a flashback, and mocking his father on his birthday during the events of Rodrick Rules. The only thing that Greg and Robert have in common is their mutual dislike of each other.

Mrs. Jefferson
Overall, Robert and his wife have a very good relationship. They are extremely over-protective of Rowley and anything related to them, and will not let any influence defame them since they do not accept any criticism from people they dislike. They have a good relationship in the sense that they baby Rowley, giving him anything he wants in his life, similarly to Manny Heffley getting spoiled by his mother.