The betrothal was announced on 26 April 2012.[1] Distant cousins, they share multiple descents from the Austrian fieldmarshal Charles Marie Raymond, Duke of Arenberg.[10] Their families are connected in several other ways: Stephanie's father, Count Philippe de Lannoy was a first cousin of Antoine, 13th Prince de Ligne, who married Princess Alix of Luxembourg — Guillaume's grand-aunt — their son Prince Antoine Lamoral married Countess "Minthia" de Lannoy, Stephanie´s second cousin once removed. Count Philippe was also a first cousin of Princess Yolande de Ligne, who married Archduke Carl Ludwig of Austria, and their child, Archduke Carl Christian of Austria (Stephanie's second cousin) married Princess Marie Astrid of Luxembourg, Guillaume's aunt.