This study traces the origin of royal blood disorders affecting Queen Victoria's descendants back 500 years to the del Balzo/de Baux family of medieval Provence (1300s-1400s). Through comprehensive genealogical analysis and inbreeding coefficient calculations, we demonstrate that systematic consanguineous marriages created cumulative inbreeding (F ≈ 0.07-0.15) in Margaret de Baux (1394-1469), 4-5 generations before Jacquetta of Luxembourg. This genetic load transmitted through Jacquetta → Elizabeth Woodville → Elizabeth of York → Margaret Tudor → Mary Queen of Scots (who married her first cousin Lord Darnley, F = 0.0625) → James VI/I (F ≈ 0.09-0.11) → eventually reaching Queen Victoria (F ≈ 0.07-0.12). The study documents reproductive failure patterns across multiple generations, including Margaret de Baux's sons (5 of 6 failed to reproduce, suggesting X-linked inheritance), and demonstrates how inbreeding coefficients approaching half-sibling levels accumulated through repeated cousin marriages. This represents one of the longest documented cases of inbreeding depression in human history, spanning 20+ generations and contributing to hemophilia and other blood disorders in modern European royalty.