aunt vs son-in-law

aunt

noun
  • The sister or sister-in-law of one’s parent. 

  • A woman of an older generation than oneself, especially a friend of one's parents, by means of fictive kin. 

  • The female cousin or cousin-in-law of one’s parent. 

son-in-law

noun
  • The husband of one's child. 

How often have the words aunt and son-in-law occurred in a corpus of books? (source: Google Ngram Viewer )