GRONINGEN, NETHERLANDS - APRIL 09: Princes Constantijn of The Netherlands arrive at the Oosterpoort for the Kingsday concert on April 9, 2018 in Groningen, Netherlands. (Photo by Patrick van Katwijk/Getty Images)
GRONINGEN, NETHERLANDS - APRIL 09: Princes Constantijn of The Netherlands arrive at the Oosterpoort for the Kingsday concert on April 9, 2018 in Groningen, Netherlands. (Photo by Patrick van Katwijk/Getty Images)