Grand Duke Guillaume and Grand Duchess Stéphanie of Luxembourg lead the glamour at a gala dinner celebrating his accession Grand Duchess Stéphanie dazzled in a diamond tiara as she supported her husband, Grand Duke Guillaume, in welcoming guests to the Grand Ducal Palace Prince Guillaume – pictured here on his wedding to Princess Stéphanie, will be named Lieutenant Representative of Luxembourg, marking the beginning of a transition of power from his father, Grand Prince Henri Andreas Rentz/Getty Images Grand Duke Guillaume of Luxembourg was born 11 November 1981 at the Grand Duchess Charlotte Maternity Hospital in Luxembourg City.