ePACT identifies duplicates based on parent action. We only know it's a duplicate if a parent re-selects the same child when they get a new request. It's possible that parents will makes mistakes and there isn't really a duplicate. When this is the case, the best course of action is to reset the members and re-invite them, explaining they need to ensure the NAME on the request and the PROFILE they select matches.
But if a parent choose to create a brand new profile for their child instead of selecting an existing one, we won't be able to tell it's a duplicate. In this case, you'll need to determine which member ID you wish to use and merge it on your REGISTRATION SYSTEM. The extra record will then be moved to the Disconnected tab on the next API Call.