The English Civil War had left resentment among some of the population about the monarchy and the penalties which had been imposed on the supporters of the Commonwealth. The South West of England contained several towns where opposition remained strong. Fears of a potential Catholic monarch persisted, intensified by the failure of Charles II and his wife to produce any children. A defrocked Anglican clergyman, Titus Oates, spoke of a "Popish Plot" to kill Charles and to put the Duke of York on the throne. The Earl of Shaftesbury, a former government minister and a leading opponent of Catholicism, attempted to have James excluded from the line of succession. Some members of Parliament even proposed that the crown go to Charles's illegitimate son, James Scott, who became the Duke of Monmouth. In 1679, with the Exclusion Bill - which would exclude the King's brother and heir presumptive, James, Duke of York, from the line of succession - in danger of passing, Charles II dissolved Parliament. Two further Parliaments were elected in 1680 and 1681, but were dissolved for the same reason. After the Rye House Plot of 1683, an attempt to assassinate both Charles and James, Monmouth went into self-imposed exile in the Netherlands, and gathered supporters in The Hague. Monmouth was a Protestant and had toured the South West of England in 1680, where he had been greeted amicably by crowds in towns such as Chard and Taunton. So long as Charles II remained on the throne, Monmouth was content to live a life of pleasure in Holland, while still hoping to accede peaceably to the throne. The accession of James II and coronation at Westminster Abbey on 23 April 1685 put an end to these hopes.
Question: Who was Charles II brother?
Answer: James, Duke of York