Traditional Confucian political theory favored strict agnatic primogeniture,[note 1] with younger sons displaying filial obedience to the eldest upon the passing of the father.
Following Lu Jia's conversion of Liu Bang to Confucianism in the early 1st century BC, Chinese dynasties observed it in theory though not always in practice.
Even worse conflicts could occur when invaders – previously observing their own rules of inheritance – began to sinicize, as happened to the 10th-century Liao dynasty.
These presented a grave problem when his eldest son died early, leaving a power struggle between a sheltered teenage grandson and his many experienced and well-armed uncles.
His own legitimacy was precariously established: a charred body was procured from the ruins of Nanjing and proclaimed to be the accidentally-killed emperor; the nephew's reign was then condemned and delegitimized and the surviving son kept imprisoned and single; and imperial records were falsified to establish the Prince of Yan as his father's favorite and as a son of the primary wife, giving him primacy over his other brothers.