co-parent vs guardian

co-parent

noun
  • Someone who shares in the parenting of a child or children, such as 

  • A godparent. 

  • A divorced or separated parent who shares custody with the other parent. 

  • A parent in a same-sex couple. 

verb
  • To act as a co-parent; to share custody of a child or children; to share in the responsibility of parenting a child or children. 

guardian

noun
  • A person legally responsible for a minor (in loco parentis). 

  • A superior in a Franciscan monastery. 

  • A person legally responsible for an incompetent person. 

  • Someone who guards, watches over, or protects. 

  • A major or final enemy; boss. 

How often have the words co-parent and guardian occurred in a corpus of books? (source: Google Ngram Viewer )