half aunt vs half-uncle

half aunt

noun

  • A half sister-in-law to one's parent. 

  • A half sister of one's parent. 

half-uncle

noun

  • A half brother-in-law of one's parent. 

  • A half-brother of one's parent. 

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