Request two different signatures from the same account/email address

Is your feature request related to a problem? Please describe.
My customers are accountants and tax preparers. Many of their clients are married and share a single email address. There does not appear to be a way to request signatures from two people who share the same email address.

Describe the solution you'd like
I would like to be able to add an account or email address as a signer more than once, with the ability to place signature fields for each instance. The first time the document is signed by the account/email address the first signature would be applied. The second time the document is signed, the second signature would be applied.

In the case of an email signature, two separate emails could be sent, or two different links could be sent in the same email.

Ideally, more than one signature could be defined for an account so that the two signers could switch back and forth between the signatures. But it would be acceptable to make the user change his/her signature before signing the second time.

Here is a mock up showing the same email address added as a signer two different times:

Describe alternatives you've considered
N/A

Additional context
If there is already a way to request two different signatures from the same account or email address, please let me know.

I am sure that this seems like an odd edge case. But it is extremely common for two spouses to share the same email address, especially when they are senior citizens or not very savvy with technology.

Start by reading the nine-comment discussion and tracing the existing signer-request flow for account and email signers, using the linked mockup as the UI reference. Done means the same account or email can be added twice, each signer instance can receive its own fields, and both signing and notification behavior are defined for the shared address case.