Through the Sphere interface your options are to leave both registrations or delete one of the registrations, preferably the most recent one.
To prevent the merge from occurring:
- Edit (BB709965) the Real Time Dedupe settings.
- Register in a way to bypass the dedupe settings: for example, if the real-time dedupe settings are first name, last name, and email address match exactly, alter one of these fields when registering.
- Create a new Kintera Thon event each year to prevent the merging of records.