surrogate

Used to indicate what is being replaced or substituted.

A woman who bears a child on behalf of another person or couple.

A man who acts as a father figure in place of the biological father.

A person who takes on the role of a parent for a child.

A child who is psychologically substituted for another person, such as a deceased sibling or an absent spouse.

To employ someone or something as a substitute.

To exist or serve as a substitute.

To perform the function or role of a substitute.

To begin to function as a substitute.