Two or more users with same email address
How can I set up daily practice for two or more users with the same email address?
Given the times I've seen people who accidentally created a second account, I think it might be possible to create two accounts with the same email address. Not sure though. If Duo won't let you create a second account with an email that has already been taken, then try creating a second account using a second email address (try a temporary account like this one) and then changing the email.
But maybe someone else has a better idea or more information.
Are you using the same email because you think you're limited to one via your internet provider? What about other email companies, like gmail?
I had assumed you were using the same email because the other person was a kid and not old enough to have their own account. If that's the case, and you think you'll be dealing with this more often, what about creating an account for the kid that you control? That could be a plan B if my earlier suggestion doesn't work.