No, I do not think that exists. The request must always come from the person who wants to die. Physician-assisted dying may not be requested by a third party.
There are, however, advance directives, that is to say situations where the request was made by the person before they lost their mental capacity. A third party can never make a request in that person's name.
I might mention a single exception, from The Netherlands. There is an agreement between physicians and attorneys that is known as the Groningen Protocol. It is mentioned in one of the documents prepared by the Library of Parliament. It discusses the euthanasia of severely disabled babies. This has not yet been included in legislation.