In hereditary monarchies, particularly in more ancient or in more underdeveloped times, seniority was a much used principle of order of succession.

%20%20%20%20Salic%20law%20%20%20%20%20%20%20... Agnatic Succession means basically the complete exclusion of females of the dynasty and their descendants from the succession. Its one form is agnatic seniority or patrilineal seniority, under which succession to the throne passes to the monarch's next eldest brother (even if the monarch has own children, sons), and only to the monarch's children (to the next generation) after males of the elder generation have all exhausted.

This rule of succession correlates closely with an idea of genealogical %20%20%20For%20distance%20between%20people%2C%20see%20proxemics.%20%20%20%20... proximity with the "original" monarch.

Succession from a brother to another brother (or otherwise within the same generation) was of necessity very useful and applied in centuries when the average lifespan even in wealthier classes (particularly in families enjoying monarch-level income) was so short that even the eldest children of a parent were not yet adults at the time of the death of the parent. This was usual when living conditions, sustenance and food were poorer, leading to early health problems, and/or when monarchs themselves participated personally much in violent activities such as warring, marauding, expeditions and duels. When the average lifespan got sufficiently increased, %20%20%20Primogeniture%20is%20inheritance%20by%20the%20first-born%20of%20the%20entirety%20of%20a%20parent%5Cs%20wealth%2C%20estate%20or%20office.%20... primogeniture began to dominate as order of succession. Primogeniture is the practical opposite of seniority, within succession principles - younger brothers are left out in favor of the first-born and the heirs of that one.

See also other succession systems such as degree of proximity, %20%20%20Tanistry%20(from%20Gaelic%20tana%2C%20lordship)%20was%20a%20custom%20among%20various%20Celtic%20tribes%2C%20by%20which%20the%20king%20or%20chief%20of%20the%20clan%20was%20chosen%20from%20among%20the%20heads%20of%20the%20septs%20and%20elected%20by%20them%20in%20full%20assembly.%20... tanistry, %20%20%20%20This%20article%20is%20about%20rotation%20as%20a%20movement%20of%20a%20physical%20body.%20... rotation and %20%20%20An%20elective%20monarchy%20is%20a%20monarchy%20whose%20reigning%20king%20or%20queen%20is%20elected%20in%20some%20form.%20... elective monarchy

Brothers succeeding each other as a system lead soon, in next generation(s), to complex patterns and also easily to disputes between branches which had thus formed inside the monarchical House. Monarchs had collateral relatives, some of which were rather distant cousins, who however were as entitled to succeed as the monarch himself. Either one branch obtained sufficient control over others (often by means of war), or the rival branches arrived in some sort of balance (such as the succession becoming rotative), or the inheritance was somehow partitioned.

Succession within one family based on seniority was often a form to control an %20%20%20An%20elective%20monarchy%20is%20a%20monarchy%20whose%20reigning%20king%20or%20queen%20is%20elected%20in%20some%20form.%20... elective Monarchy. At least those two forms of monarchy (agnatic seniority and elective monarchy) were mostly used in same centuries. Most kingdoms were officially elective long into the historical times (though the election usually, or always, fell to family of the deceased monarch).

Preference for males, existing in most systems of %20%20A%20hereditary%20monarchy%20is%20the%20most%20common%20style%20of%20%20%20monarchy%20and%20is%20the%20form%20that%20is%20used%20by%20almost%20all%20of%20the%20world%5Cs%20existing%20monarchies.%20... hereditary succession comes mostly from the perceived nature of the tasks and role of the monarch: A monarch most usually was, firstly and foremostly, a military protector.

• His income was very dependent on protection money collected from those people he was in office of protecting against wars, violence, crimes, other injustices (already in those times, this sort of protection money, more or less extorted from people by use or threat of the violent powers of the protector himself, was labelled by the less-infuriating terms "tax" and "duty", and as we all know, those forms of revenue-collecting have continued into our less-monarchical governments, too).
• It was very useful, or even requisite, that the monarch be a warrior, and a commander of military. And, also, war troops (consisting typically only of males) were perceived to approve only males as their commanders, or even warriors.
• Additionally, in some monarchies (such as France), the monarch held a certain mystical position, some task best described as priestly position (high priest or demigod). That sort of position was, depending on the tradition in question, often denied of females. In the French monarchy, one of the official explanations for the %20%20%20%20%20%20%20%20The%20King%20of%20the%20Franks%2C%20in%20the%20midst%20of%20the%20Military%20Chiefs%20who%20formed%20his%20Treuste%2C%20or%20armed%20Court%2C%20dictates%20the%20Salic%20Law%20(Code%20of%20the%20Barbaric%20Laws).--... Salic Law was that the monarch was obliged to use certain sacred instruments, which females are forbidden even to touch.

Basically, we can imagine a system of cognatic seniority, allowing female siblings to succeed their siblings as monarchs. However, no known monarchy has consistently used such order of succession. Perhaps the reason has been that seniority has been used in such centuries and in such societal situations that females were regarded as too lowly or otherwise impossible.

Agnatic seniority has been used in several historical monarchies, for example in %20%20%20The%20Russian%20Federation%20(%20%20Russian%3A%20%26%231056%3B%26%231086%3B%26%231089%3B%26%231089%3B%26%231080%3B%26%23769%3B%26%231081%3B%26%231089%3B%26%231082%3B%26%231072%3B%26%231103%3B%20%26%231060%3B%26%231077%3B%26%231076%3B%26%231077%3B%26%231088%3B%26%231072%3B%26%23769%3B%26%231094%3B%26%231080%3B%26%231103%3B%2C%20%20%20transliteration%3A%20Rossiyskaya%20Federatsiya%20or%20Rossijskaja%20Federacija)%2C%20or%20Russia%20(Russian%3A%20%26%231056%3B%26%231086%3B%26%231089%3B%26%231089%3B%26%231080%3B%26%23769%3B%26%231103%3B%2C%20transliteration%3A%20Rossiya%20or%20Rossija)%2C%20is%20a%20country%20that%20stretches... Russia during the %20%20%20%20Rurik%20Dynasty%20%20%20%20%20%20%20... Rurikid Dynasty. Nowadays, it is used at least in the monarchy of %20%20%20%20The%20Kingdom%20of%20Saudi%20Arabia%20is%20a%20country%20on%20the%20Arabian%20Peninsula.%20... Saudi Arabia.