niece vs son-in-law

niece

noun
  • A daughter of one’s cousin or cousin-in-law 

  • A daughter of one’s sibling, brother-in-law, or sister-in-law; either the daughter of one's brother ("fraternal niece"), or of one's sister ("sororal niece"). 

son-in-law

noun
  • The husband of one's child. 

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