Professor Francis John Byrne of University College Dublin also identified an indfine system used in some clans before the year 1000, with membership going back to a common great-great-great-grandfather, perhaps necessary at a time of frequent warfare.
[citation needed] In the European context, membership of a derbfine was similar to holding the rank of prince du sang in France.
The inheritance of the Norman royal line on the death of Stephen, King of England and his succession by his cousin, Henry II, is similar.
Stephen's son was disinherited by consent, and Henry was chosen as the equivalent of tánaiste or next chieftain and succeeded to the English throne in 1154.
The system was again attempted during the incapacity of Henry VI of England, when the House of York obtained the support of some royal cousins to take the throne in 1461.