Joe Heffley

Joe Heffley is the younger brother and rival of Frank Heffley, brother-in-law of Susan Heffley, and uncle of Greg, Rodrick and Manny Heffley.

Role in Rodrick Rules
Joe comes to Greg's house late for Thanksgiving. His children all call their uncle "Aunt Fwank (Frank)". Susan says that this is cute but Frank says that Joe taught them to do that. When Frank goes down to the basement, to do edits to his Civil War diorama, Joe sneaks down and says "Nice toys, big brother!". Frank explains everything to Joe, but Joe didn't listen to a syllable he was saying. Greg mentions that the year before that book takes place, Manny was approximately 2 weeks from getting out of diapers, but Joe puts a stop to it by saying "Watch out for the 'potty monster', little fella!". Every-time time Frank had to change a dirty diaper after that, he started cursing Uncle Joe under his breath.

Role in The Last Straw
Joe makes a brief appearance on The Party at the gym. Greg says that when the songs start, he holds Greg's hands, even though he doesn't have to. Greg also says he has an iron grip.

Role in Dog Days
Greg says he asked Joe to encourage Frank to buy a dog. Joe slaps Frank's back saying "A boy needs a dog!". Later, he is at Greg's birthday party, and his dog, Killer, eats some of Greg's birthday cake.

Role in The Ugly Truth
Joe and his brother, Frank, are trying to get Greg to be more responsible and not end up like their brother, Gary Heffley. He appears at Gary's Last wedding and the Heffley family reunion.

Personality
Uncle Joe is evidently the most troublesome character in the series, who inadvernteley embarrasses, harms and wreck's Frank's family, by causing lots of pain and disgust. Uncle Joe is classified as very immature, childish, overly-affectionate and troublesome.

Appearance
Uncle Joe is shown having a Mexican-style mustache, black hair and western-style clothing, looking more like a cowboy in Greg's illustrations.

Trivia

 * Even though Uncle Joe is younger than Frank, the illustration of his mustache and other features may imply that Uncle Joe is older than what Greg's portrays him to be.
 * Uncle Joe is quite possibly the only character to be universally disliked by Greg, Rodrick, Frank and Manny.
 * The Ugly Truth is the only book in which Uncle Joe appears in and gets along with Frank.