In terms of inheriting the British throne, the same rule applies to twins as to single children – the firstborn inherits. Even if the first child is only minutes older than the younger, he or she still takes the prize.
We have not yet had twins in line to the British throne. Twins are an increasingly common occurrence in 21st-century Britain but rare in history, chiefly because medical science was not sufficiently progressed to cope with the complications of a twin pregnancy.
Previously, in Britain, the eldest son inherits the throne, so if the twins had been a male and female pair, the male would inherit, regardless of birth order.
In 2013, the abolition of royal primogeniture was confirmed. So, if a royal bears twins in the future, and the elder is female, then she could one day be queen.
The Marquess of Cholmondeley became a father of twin boys in 2009 and the firstborn, Alexander, Earl of Rocksavage, inherits the extensive estates and titles. The younger son, Lord Oliver Cholmondeley, must find another path in life.
One day, twins will probably be in the line of succession. Possibly – a strange thought – an identical pair.
Answered by presenter and historian professor Kate Williams
This article was first published in the February 2013 issue of BBC History Magazine