A Shecky is the lesser-known sibling of a famous person. They come from the same gene pool, but clearly lack that "something special" to elevate them out of Sheckyhood. Additionally, they are granted singing/acting opportunities strictly based on genetic nepotism (i.e. See Ashlee Simpson).
Ashlee Simpson = Shecky Simpson
Kevin Dillon = Shecky Dillon
Chad Lowe = Shecky Lowe