Lewis was born before 1270, son of Louis de Brienne and Agnès de Beaumont-au-Maine and grandson of John of Brienne, King of Jerusalem by his third wife, Berengaria of Leon, making him a second cousin of Edward II.
The lineage of Lewis revealed connections to prominent figures, including Louis de Brienne and Agnès de Beaumont-au-Maine, making him a descendant of John of Brienne, King of Jerusalem by his third wife, Berengaria of Leon, which in turn linked him to Edward II as a second cousin.