blood brother vs kin

blood brother

noun
  • 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. 

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

kin

noun
  • Relationship; same-bloodedness or affinity; near connection or alliance, as of those having common descent. 

  • Race; family; breed; kind. 

  • Persons of the same race or family; kindred. 

  • One or more relatives, such as siblings or cousins, taken collectively. 

  • A fictional character who one deeply relates to. 

  • Someone who relates deeply to a certain fictional character. 

adj
  • Related by blood or marriage, akin. Generally used in "kin to". 

verb
  • To identify with; as in empathize or emotionally relate to a fictional character. 

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