lastborn vs younger

lastborn

noun
  • The youngest child of a family. 

  • The youngest member of any company or organization. 

adj
  • Born last in a family; youngest in a the family. 

  • Younger than anyone else in a group. 

younger

noun
  • One who is younger than another. 

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