Our company also needs this. Our case is slightly different:
We are a music school, and a lot of our students are minors who either don’t have their own email addresses. Thus we need to send bulk emails to student, but for the email to go to the parent as well. We have organized our Hubspot so that:
Student is a contact with custom property: Student=yes
Parent is a contact with custom property: Payer=yes
Both contacts are associated to a company which represents the family, as the contacts can not be directly associated to one other.
Bunp this up hubspot - this is something you clearly need to deliver. I will look into the ZOHO option as well. I am tired of Hubspot being so insanely expensive and non-responsive to customer needs.