sibling family
n.— «Mullins’s film follows two “sibling families”: families where both parents have died from AIDS and so the eldest children must take care of the younger.» —“AIDS Documentaries Want You To Fight Back” by Brian Gibson Vue Weekly (Edmonton, Alberta, Canada) Nov. 30, 2006. (source: Double-Tongued Dictionary)
Further reading
Quiz Guy John Chaneski was inspired by a version of film in which a filmmaker went to the trouble to take a clip of every word used in the movie The Wizard of Oz, arranging them in alphabetical order, all the way to the Tin Man’s saying zipper...