If I understand you correctly, I think the same thing happened with my brother: I created a profile and used it to send him an invitation. He misplaced the email and simply joined as a new member, so he had two profiles. I was the profile manager for one, and he managed the other. We simply merged the duplicate profiles.
I then removed myself as profile manager from his profile, but I'm still on his trusted list, and I think I also bulk-added him to the trusted list for various profiles on my watchlist.
Is that the same situation you and your cousin are facing, or am I missing something?