Robert Jefferson

Robert Jefferson is father of Rowley Jefferson, and the husband of Ms. 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. In Dog Days, Robert takes a close interest in sports, such as tennis and golf.

Personality
He is more shrill than Frank Heffley, and he is far more temperamental, rude, irritable, paranoid, disciplinary, strict and short-tempered, yet he 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. He sees Greg as a bad influence for several reasons. Examples include Greg's haunted house idea, insulting him by calling him a woman at dinner while trying a "secret language," and mocking his father on his birthday. He is extremely rude and cannot accept criticism, as seen in Diary of a Wimpy Kid: Dog Days, where he banishes Greg out of the country club simply for stating several complaints about the quality of service, and how they can be improved.

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.