family tree vs heirship

family tree

noun
  • The totality of someone's ancestors and offspring 

  • A diagrammatic representation of a pedigree, illustrating the connections between a person's ancestors, offspring and other relatives 

heirship

noun
  • The status of being heir to something or someone 

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