adding more then one email account to memberID

[charmed_ones]

The App has memberID and one email address that is used to log in to that Member's Records. The Issue I have is some clients have three or four different people needing access to the information for the same memberID.

Is there any way with hooks or custom code that I can have another table with other users for the same memberID and their own email connected to that memberID and their own password?

I've been searching and searching and can't seem to find a way to allow more than one member to log in per memberID

Thanks in advance for any help you can direct me too.