There are several ways to link guests so they share a bidder number:

• Link automatically at ticket sale by creating a Couples ticket and checking the box "Share one bidder number for all guests on this ticket (Auto Linking)?"  
  
• Link/unlink prior to event from Ticket Page or Site Settings (shown below)
• Link during check-in.

Note:  guests cannot be linked/unlinked once they have checked in.   If you are certain they have not placed any (paper) bids using their bidder number, you can undo check-in on the Ticket Page (see below).