fathership vs stepfather

fathership

noun
  • The state of being a father; fatherhood; paternity. 

  • A title of respect addressed to a priest. 

stepfather

noun
  • A husband of one's parent distinct from one's biological father 

  • A husband of one's biological mother after her initial marriage to or relationship with one's biological father. 

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