folks vs sibling

folks

noun
  • The members of one's immediate family, especially one's parents 

  • People in general; everybody or anybody. 

  • The police. 

  • Late 19th and early 20th century migrants to California from Iowa and other parts of the Midwestern United States. 

sibling

noun
  • A person who shares a parent; one's brother or sister who one shares a parent with. 

  • A node in a data structure that shares its parent with another node. 

  • The most closely related species, or one of several most closely related species when none can be determined to be more closely related. 

How often have the words folks and sibling occurred in a corpus of books? (source: Google Ngram Viewer )