co-parent vs stepmother

co-parent

noun
  • A parent in a same-sex couple. 

  • A godparent. 

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

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

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. 

stepmother

noun
  • The wife of one's biological father, other than one's biological mother. 

  • A viola, especially Viola tricolor, heartsease. 

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