Dutch infantry at the Battle of Oudenarde, the Siege of Lille, and the Battle of Malplaquet. The prestige that he acquired from his military service should have favored his eventual elevation as stadtholder in the remaining five provinces. However, in 1711, when traveling from the front in Flanders to meet the King of Prussia in The Hague in connection with his suit in the succession dispute, he drowned on 14 July when the ferry boat on the Moerdyk was overturned in heavy weather. His son was born six weeks after his death. Marriage and issue On 26 April 1709, he married Princess Maria Louise of Hesse-Kassel (1688–1765), daughter of Charles I, Landgrave of Hesse-Kassel, and granddaughter of Jacob Kettler, Duke of Courland. They had two children. Common ancestor of hereditary European monarchs Between 9 April 1939 and 18 May 1941 and again between 31 July 1943 and 8 September 2022 John William Friso and Maria Louise were the most recent common ancestors to all reigning European monarchs. Between 18 May 1941 and 31 July 1943 the puppet Independent State of Croatia was a kingdom under Prince Aimone, Duke of Aosta (his regnal name was Tomislav II) in opposition to the exiled monarchy under Peter II of Yugoslavia. Peter and Aimone's wife Irene descended from John William Friso and Marie Louise, but not Aimone himself, so the position of royal MRCA was held by John Frederick, Margrave of Brandenburg-Ansbach (1654 – 1686), who held the distinction alone since the descents came from both his marriages. Before 9 April 1939 King Zog I of Albania makes the position of MRCA unknown, since his ancestry is itself almost entirely unknown and he has no traceable connection to other European royalty except through his wife Geraldine. Since the death of Elizabeth II on 8 September 2022 the MRCA of hereditary European monarchs is John Frederick's great-grandson Louis IX, Landgrave of Hesse-Darmstadt (1719 – 1790) and his wife Caroline of Zweibrücken (1721 – 1774), who were formerly common ancestors to all reigning European monarchs except Elizabeth II. This is because Charles III is descended through his paternal grandmother from Louis IX's grandson Louis II, Grand Duke of Hesse via both her parents. Despite this, John William Friso and Marie Louise remain to be the most recent common ancestor of all current and former European monarchs. Legacy Monuments in Moerdijk and Strijensas, on both sides of