Agnatic seniority

Agnatic seniority is a patrilineal principle of inheritance where the order of succession to the throne prefers the monarch's younger brother over the monarch's own sons. A monarch's children (the next generation) succeed only after the males of the elder generation have all been exhausted. Agnatic seniority essentially excludes females of the dynasty and their descendants from the succession. Contrast agnatic primogeniture, where the king's sons stand higher in succession than his brothers.

In hereditary monarchies, particularly in more ancient times, seniority was a much-used principle of order of succession. The Ottoman Empire evolved from an elective succession (following the principle of agnatic seniority) to a succession inherited by the law of agnatic seniority.

In succession based on rotation (close to seniority), all (male) members of the dynasty were entitled to the monarchy, in principle. However, this tends to lead to situations where there is no clear rule to determine who is the next monarch.

Brothers succeeding each other as a system leads quickly, particularly in the following generations, to complex patterns and also to disputes between branches which have formed within the monarchical house. Monarchs had collateral relatives, some of whom were rather distant cousins, who were often as entitled to succeed as the monarch himself. Either one branch obtained sufficient control over others (often by force), the rival branches arrived at a balance (such as the succession becoming rotational), or the inheritance was somehow partitioned.

Succession based on agnatic seniority or rotation was often limited to those princes who were sons of an earlier reigning monarch. Thus a son of a king had a higher claim than a son of a prince. In some cases, distinctions were even made based on whether the claimant was born to a monarch who reigned at the time of birth (porphyrogeniture).

This limit was practical, as otherwise the number of rivals would be overwhelming. However, it usually left more than one rival who too often waged civil war against each other. In other cases, the eligible branches of dynasty became extinct in the male line (no surviving sons), in which situation the limit was problematic.

Sons of princes who did not live long enough to succeed to the throne were of course unsatisfied with such limits. This led to interpretation problems: What if a claimant's father was a rightful monarch, but not recognized by everyone, or by no one (did not rule at all)? The cases were further complicated by co-reigning monarchs, but this was often a practical solution to a controversial succession.

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