 Uncertainty exists around the birth of du Casse.Though he is usually said to have been born on 2 August 1646 in Saubusse, near Dax (Landes), the son of Bertrand Ducasse, a Bayonne ham merchant, and Marguerite de Lavigne, he was actually born in Pau to Jacques Ducasse and Judith Remy.His father Jacques was the son of Gaillard Ducasse, a minister in the Reformed Church of France, which designated the family as Huguenots.