I thought it seems unlikely that there were only 2 especially as there have been numerous times that brothers have been kings making it impossible to be descended from both. Where's the question from JC?
Some of the answers given are plainly wrong. For instance through the Bowes Lyon family Charles will be descended from Charles I through to his son Charles II and then through a number of Charles illegimiate sons all of whom married into the British aristocracy. He may well also be descended from some of James II illegitimate children as well.