As you know it's possible to add multiple emails to your main PayPal account. Is there any way to tell those 2 emails belong to the same person without sending or receiving money? Before you could tell by checking someone's Membership Info and see their main PayPal email, but this is no longer possible because PayPal disabled it.
You can add multiple emails for receiving perpose only. You can not send paypal by all Emails. You all payments will go through primary E-mail.