surrogate

One that takes the place of another; a substitute.

A person or animal that functions as a substitute for another, as in a social or family role.

A surrogate mother.

In Freudian psychology, a figure of authority who takes the place of the father or mother in a person’s unconscious or emotional life.

A judge in New York and some other states having jurisdiction over the probate of wills and the settlement of estates.

Substitute.

To put in the place of another, especially as a successor; replace.

To appoint (another) as a replacement for oneself.

To put in the place of another; substitute.