blood brother vs relation

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. 

relation

noun
  • A member of one's extended family; a relative. 

  • The manner in which two things may be associated. 

  • A set of ordered tuples. 

  • A set of ordered tuples retrievable by a relational database; a table. 

  • The act of intercourse. 

  • Specifically, a set of ordered pairs; a binary relation. 

  • The act of relating a story. 

  • A statement of equality of two products of generators, used in the presentation of a group. 

  • A subobject of a product of objects. 

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