In a lesbian couple, the nonbirth mother (partner of the birth mother) of a child, especially one who takes an equal role in mothering the child.
In polygamy, the relationship between one co-wife and another, in respect to their children.
In polygamy, a wife of one's father who is not one's mother; that is, co-wife of one's mother.
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
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.