relative vs relative-in-law

relative

noun
  • Someone in the same family; someone connected by blood, marriage, or adoption. 

  • A type of adjective that inflects like a relative clause, rather than a true adjective, in certain Bantu languages. 

adj
  • Expressed in relation to another item, rather than in complete form. 

  • Having the same key but differing in being major or minor. 

  • Connected to or depending on something else; comparative. 

  • Depending on an antecedent; comparative. 

  • Relevant; pertinent; related. 

  • Capable to be changed by other beings or circumstance; conditional. 

relative-in-law

noun
  • A relative of one's generation, separated by one degree of marriage. 

  • Co-relative-in-law: A relative of one's generation, separated by two degrees of marriage. 

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