co-parent

Short definition from Wiktionary

Noun

1. 1
   Someone who shares in the parenting of a child or children, such as
2. 2
   Someone who shares in the parenting of a child or children, such as: A godparent.
3. 3
   Someone who shares in the parenting of a child or children, such as: A divorced or separated parent who shares custody with the other parent.
4. 4
   Someone who shares in the parenting of a child or children, such as: A parent in a same-sex couple.
5. 5
   Someone who shares in the parenting of a child or children, such as: A parent in a platonic friendship with the other parent.

Verb

1. 1
   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.