(L-R) Belgium's Princess Elenoire, Prince Gabriel and Prince Emmanuel attend the National Day Ceremony in front of the Royal Palace in Brussels, Belgium, 21 July 2021. The Belgian National Day celebrated annually on 21 July marks the day that King Leopold I of Saxe-Coburg-Saalfeld took the oath as first king of the Belgians in 1831 ? Olivier Polet queen mathilde, king philippe, Prince Laurent, princess astrid,