Although some of Charles ' children made claims to the throne , most notably his first son James Scott , 1st Duke of Monmouth , their illegitimacy meant that after Charles ' death , his brother James , Duke of York became king instead . Although some of Charles ' children made claims to the throne , most notably his first son James Scott , 1st Duke of Monmouth , their illegitimacy meant that after Charles ' death , his brother James , Duke of York , became king instead .