Are they your most important relatives? We are living in what has been called the Great Cousin Decline. Some think losing cousins could come to affect every stage of our lives.
Cousin crash as UK families shrink
Cousin trouble: Britain's Prince Louis is "encouraged" to be quiet by his second cousin Savannah Phillips — the granddaughter of the King's sister Princess Anne. Glossary
BBC - The British Broadcasting Corporation is the UK's national broadcaster.
William I - Better known as William the Conquerer. He invaded England with his Franco-Norman army and became king of England in 1066.
Edward the Confessor - The king of England from 1042 to 1066.
Norman - The Normans were vikings who settled in northern France. They colonised parts of Europe.
Fertility rates - The number of children born, on average, to each woman within a studied group. A total fertility rate of 2.1, is the minimum needed for a population to remain steady and is known as the "replacement rate".
Generation - A big group of people who were all born at the same time.