Sui generis
A similar case that led to the use of the label "sui generis" is the relationship of New Caledonia relative to France, because the legal status of New Caledonia can aptly be said to lie somewhere between a French overseas collectivity and a sovereign nation. Although other examples of such status for other dependent or disputed territories may exist, this arrangement is unique within the French realm.
Order of succession
Proximity of blood is a system wherein the person closest in degree of kinship to the sovereign succeeds, preferring males over females and elder over younger siblings. This is sometimes used as a gloss for "pragmatic" successions in Europe; it had somewhat more standing during the Middle Ages everywhere in Europe. In Outremer it was often used to choose regents, and it figured in some of the succession disputes over the Kingdom of Jerusalem. It was also recognized in that kingdom for the succession of fiefs, under special circumstances: if a fief was lost to the Saracens and subsequently re-conquered, it was to be assigned to the heir in proximity of blood of the last fief-holder.