blood brother vs consanguinity

blood brother

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

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

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

consanguinity

noun
  • A consanguineous or family relationship through parentage or descent. A blood relationship. 

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