aunt vs blood brother

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. 

blood brother

noun
  • A brother by blood: a brother-german or half-brother, as distinguished from step-brothers. 

  • An unrelated male considered to share such a strong relationship generally. 

  • An unrelated male considered to share a brother-like relationship established by a ceremonial sharing of blood in some cultures. 

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