primogeniture (and its polar opposite: Ultimogeniture). In a
perfect world these systems would have prevented disputes
over succession with rulership passing from parent to child in
an unbroken line. However, it was not (and is not) a perfect
world and sometimes other factors intervened.
For instance; it was not entirely settled who succeeded to the
throne if a ruler died with no direct heirs. It was firmly
established that brothers (or sisters) could inherit in that
instance but once you moved out to having to consider uncles,
cousins, and nephews primogeniture faced a challenge. This
challenge was Proximity of Blood.
Proximity of Blood
succession by looking at who the closest living relative to the
deceased monarch was. It differs from Primogeniture in that
successional representation was not observed. Which is to say
living relatives were not counted as 'representing' their
ancestors. A graph may be helpful here.
crown marks the recently deceased king with no direct heir.
Both Primogeniture and Proximity of Blood track back to the
great grandfather and down the line of his second-born (the
deceased king's great uncle). This great uncle had two
children with his eldest having died leaving behind one child
(the deceased king's second cousin). The younger son of this
great uncle (the deceased king's first cousin once removed) is
Under primogeniture the second cousin stands in for their
parent, who as firstborn would inherit. Under Proximity of
Blood all that matters is that the first cousin once removed is
one step closer related to the deceased king and would inherit
under this system.
As you may be realizing such conflicting claims could easily
lead to war. And they did. It should also be noted that a
major flaw with using Proximity of Blood to determine
succession is that you could have a situation where there are
multiple people equally related to the previous king.
Proximity of Blood was a key factor in Robert the Bruce
becoming King of Scotland. It was also an important element in the succession of the Crusader Kingdoms since parts of the
kingdom might be lost to the Saracens and then regained
later. The Netherlands still uses Proximity of Blood today but
only to determine the collateral royal lines.
A Kisaragi Colour