aunt vs blood relative

aunt

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

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

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

blood relative

noun
  • A person who is related to another through a common ancestor, and not merely by marriage or adoption. 

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