Their counterparts. Like Captain van Donselaar is on the Eurodam; Captain Scott is on the Noordam & Captain Schoonderbeek is on the Prinsendam, so that's who was "driving" those ships
Captain Mateboer (Noordam), Captain Mercer (Eurodam), Captain Gunderson (Prinsendam) were at the ceremonies.
I couldn't hear the names of most of the Captains very well as they were introduced even though I had my speakers turned as high as I could get them, but I did hear some of them.