Rules governing the succession of kings and queens, should the incumbent monarch abdicate or die. In the UK, royal succession is based on rules determined in the seventeenth century, especially the Bill of Rights (1689) and the Act of Settlement (1701). The coming marriage of Prince William and Kate Middleton has prompted debate about changing the rules, as any boys the couple give birth to will take precedence in the line or royal succession to the girls, regardless of age. Changes may also be made to allow marriage or succession of Roman Catholics.