Angular 9 / Angular Material - formArrayName in formArrayName

I use Angular Material in my project and I have this form:

this.form = this.formBuilder.group({    
    addresses: this.formBuilder.array([]),
    contactPersons: this.formBuilder.array([])
});

addresses looks like this:

let address = this.formBuilder.group({
  address: this.formBuilder.group({
    street: ['Street Number 1', [Validators.minLength(2)]],
    ...
  }),
  contactPersons: contactPersonsArray
});

This means that I have contactPersons at two different places. My question now would be how to access contactPersons in address?

I have tried this:

<div formArrayName="addresses">
    <div *ngFor="let address of addresses.controls; index as i" [formGroup]="address">
         <div formArrayName="address.contactPersons"> // address.contactPersons does not work
               Amount of contact persons {{address.contactPersons.length}}: 
         </div>
         <div formArrayName="contactPersons"> // I also tried this but here contactPersons from outer address is taken

[EDIT] I have solved my problem, the solution to acces contactPersons within addresses is

form.controls.addresses.controls[i].controls.contactPersons.controls

Why it is so complicated to access objects/arrays with Angular Material is a mystery to me - maybe I have a worse overview.