Kyle is said to be based on series co-creator Matt Stone, who also provides the character's voice. Like Kyle, Matt Stone is Jewish and Kyle's parents, Gerald and Sheila, are named after Matt's. Along with Stan Marsh, Eric Cartman, and Kenny McCormick, Kyle is one of the main characters on the show. In the early seasons of South Park, Kyle was very similar to Stan. In later seasons he began to differentiate himself through his short temper, especially when dealing with Cartman's anti-Semitism. Despite his ill temper, Kyle is shown to be a good student, probably the best of the four boys.
The Broflovskis are the only Jewish family in South Park, though they go to a well-attended synagogue, presumably in a nearby town. In the season three episode "Jewbilee" Kyle is shown to be part of the "Jew Scouts" along with many other Jewish children. Kyle occasionally has crises of faith, such as when he developed a hemorrhoid while Cartman inherited enough money to buy his own amusement park, and after viewing Mel Gibson's Passion of the Christ convinced him that Jews killed Jesus and should issue an official apology.
Kyle has a younger brother, Ike Broflovski. Ike is a Canadian toddler, though Kyle didn't realize he was adopted until the season 2 episode "Ike's Wee Wee." In the episode, Kyle tries to save his little brother from getting circumcised. Kyle is shown to be protective of Ike, including stopping him from using flavored vapes, and having a nightmare that a Family Guy-inspired terror attack kills him. Kyle's mother Sheila is overprotective of her sons, and has taken up causes to prevent the toilet humor of the boy's favorite show, Terrance and Phillip, from influencing them negatively. Kyle's father Gerald is the top (and perhaps only) lawyer in South Park. Kyle has a cousin, also named Kyle, who is a nasally hypochondriac that causes Kyle great embarrassment.
In The Stick of Truth, Kyle was the basis for an entire class, simply named "Jew." In The Fractured But Whole, Kyle's cousin Kyle appears as an enemy. Upon defeat, Cousin Kyle calls upon his Aunt Sheila to fight the player instead.