In the film, Uncle Seymour lost both of his legs to diabetes. Jim Barone (Seymour) actually lost both of his legs to diabetes in 2012.
Jared Sandler, Adam Sandler's nephew is the neighbor Jared.
Seymour (Jim Barone) is 87 years old. In reality, Barone is 57 years old, a mere four years, and six years older than Chris Rock and Adam Sandler, respectively.
"Lustig", the last name of Adam Sandler's character, means "funny, amusing, comical", et cetera in Swedish and German.
In the film, it is mentioned that Seymour lost his legs due to diabetes. That is true of Jim Barone, the legless actor who plays Seymour - infections that wouldn't heal due to his diabetes led to the double amputation.