"IRISH TWINS"

Irish twins is a slang term that refers to siblings born 9 to 12 months apart - usually in the same calendar year, or who are in the same class in school. The term is considered both endearing and misguided (for instance, Irish birthrate is about same as USA birthrate, see birth rate). It references a perception about families of Irish Catholics who may not use birth control (and thus may have children in quicker succession), but it is often used endearingly by the families of the "twins" themselves.