Email is each account's login identifier, so a parent account and a learner account can't be registered under the exact same address — if a family only has one real inbox (common with younger students who don't have their own email yet), you need two distinct-looking addresses that still land in the same place.

The simplest fix is Gmail's "+alias" trick: parent@gmail.com and parent+student@gmail.com (or any suffix after the +) are treated as two different addresses by Wise's registration and login forms, but Gmail delivers both to the exact same inbox, so no second real account is needed. This only reliably works on Gmail addresses — other providers don't consistently support the same trick. See also 15.5, which uses the same alias approach for a different purpose (admin test accounts).