A divorced or separated parent who shares custody with the other parent.
A godparent.
A parent in a same-sex couple.
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.
A sister-in-law of one's mother; the wife or ex-wife of a maternal uncle.
A sister of one's mother.
A similar great aunt, etc.