Diane Harmon

Diane McKenzie Harmon is Jack's cousin and birthday twin. She is introduced in fanon Season Three. She is the captain and soloist of Musical Rush (later Higher Ranges) at her school, Broadway Arts, in Syracuse, New York. She is every bit like her cousin with a much more volatile temper. She is played by singer/actress Victoria Justice.

Personality
Diane can best be described as "Jack with estrogen" and having a mouth like a trucker. She is paranoid that someone will usurp her position at school and in life. This, along with her backstabbing surroundings, have produced a cutthroat young woman who is willing to do anything to win.

However, Diane is not without her positive qualities. She cares about her cousin, claiming he's probably to only person who understands her drive and ambition as well Jenn McGraw, who she befriends during her brief stint in New Directions.

Family

 * Roger Harmon (father)
 * Kristin Harmon (mother)
 * Taylor Harmon (brother)
 * Vanessa Harmon (sister)
 * Pierce Kelsey Harmon (nephew, via Taylor)
 * Robert Harmon (paternal grandfather; deceased)
 * Kate Harmon (paternal grandmother; deceased)
 * Amelia Harmon (paternal grandaunt; deceased)
 * Leo Harmon (paternal first cousin once removed, via Amelia)
 * Kristopher Harmon (paternal uncle)
 * Juliet Harmon Paxton (paternal aunt)
 * Edward Harmon (paternal uncle)
 * Karen Harmon (paternal aunt)
 * Shane Harmon (paternal uncle)
 * Frank Harmon (paternal cousin, via Edward)
 * Special Agent Carl Harmon (paternal cousin, via Edward)
 * Bianca Munson Webster (paternal cousin, via Karen)
 * Jared Montgomery (paternal cousin, via Karen)
 * Jack Harmon (paternal cousin, via Kristopher)
 * Davis Paxton (paternal cousin, via Juliet)
 * Jude Paxton (paternal cousin, via Juliet)
 * Katie Harmon (paternal first cousin once removed, via Leo)
 * Leah Harmon (paternal cousin, via Shane)
 * Kendall Harmon (paternal cousin, via Shane)
 * Jamie Harmon (paternal cousin, via Kristopher)
 * Bobby Harmon (paternal cousin, via Shane)

Songs

 * The Ballad of Jack and Diane (with Jack; Hold on to Sixteen)
 * Finally Falling (Hold on to Sixteen)
 * ABC (with New Directions; Hold on to Sixteen)
 * Shake Up Christmas (with Jack, Dylan, Ethan, Millie, Mitchell, Michelle, Alex and Jenn)
 * Let's Stay Together (with Alex Hawthorne; Getting Married Today)
 * Dirty Diana (Michael)
 * The Warrior (with Higher Ranges; Nationals)
 * I'm on Fire (with Drew Markley; Nationals)
 * Make It in America (Nationals)
 * Man, I Feel Like a Woman (with the Trouble Tones; Internationals)
 * Keep Christmas With You (with the Harmon family; Glee, Actually)
 * Grown-Up Christmas List (with Jack and Pediatric Ward Kids; Glee, Actually)

Trivia

 * This is the second time Victoria Justice and Daniella Monet have played sisters
 * Despite playing characters that were born on the same day, Aaron Tveit and Victoria Justice were born nearly a decade apart.
 * She has a nephew, making her (and her sister) the first character in her generation to become an aunt. Jack is a step-uncle to Beth, though this is rarely mentioned as Beth is being raised by Shelby and Jared has a step-niece and step-nephew via Bianca's marriage to Stan Weber.
 * Victoria's fellow Victorious co-star Ariana Grande also has a role in the HarmonVerse, as Jennifer McGraw.
 * Trevor Rayburn's half-sister, Alyssa, is married to Diane's brother, Taylor.