Embedded document throws duplicate key error

I’m working with Mongodb and Nest Js.I have 2 schema X and Y. In X there is a property

export class X{

which stops duplicates for the same email when try to create a document of X.

And In schema Y, X is embedded in Y schema. I have this in Y schema

export class Y{
name : string;

x : X 

Now When I create first Y document with X it creates, but when I try to create an other Y with different name , but with same X document, the property email in the X schema throws E11000 duplicate error.

I’m just embedding the X, i’m not creating a new X document, Why it is throwing error when I try to create Y document, why the email unique, is effecting Y schema, while I’m just simply embedding it.

I know by referencing X in Y solves the problem. But I want to embed X.
Is there a way to stop mongo to create unique index in the Y collection of the X property?