Add additional parents by STUDENT, not by PARENT!

I have been trying to add additional parents to accounts, but I'm running in to this problem. In your steps, it has me add a parent to the PARENT's name.

I have several cases in which an additional parent wants access to pay on an account, but there is another child on the account of the parent.

For example, a mother registered her daughter and her step-daughter for dance. The mother wants to give access to the step-daughter's biological mother to help pay for her account ONLY. But I can't assign an additional contact to THE STUDENT. I HAVE TO ASSIGN ADDITIONAL PARENTS TO THE PARENT! Are you saying that when the biological mother signs in, she will be able to see account information for BOTH dancers (the daughter and step-daughter)? Because the mother who signed the two dancers up doesn't want the birth mother to see how much she is paying for her own daughter to dance. I want to assign a second parent to JUST THE STEP-DAUGHTER. I do not want the additional parent to receive statements for the daughter that isn't hers!

I have another instance in which a mother wants to allow her ex-husband to be able to have the ability to pay on the account of ONE of her children (the only child she shares with the ex-husband). If I add him, will the ex-husband also be able to see the account information for her other children that don't belong to him? The mother doesn't want him to have that information.

Yes, I could tell them to start separate accounts for their children, but then they won't receive the automatic family discount.

Please find a way to assign additional parents to the STUDENTS, not the PARENTS. It makes no sense.