By this point, it had become obvious that the queen, Catherine of Braganza, was barren and would never produce an heir, making the king's brother, James, Duke of York heir to the throne, which worried Ashley because he suspected that James was a Roman Catholic. Ashley and Buckingham urged Charles to declare his illegitimate son, the Duke of Monmouth, legitimate, as did Charles Howard, 1st Earl of Carlisle. When it became clear that the king would not do so, they urged him to divorce Catherine and remarry. This was the background to the famous Roos divorce case: John Manners, Lord Roos had obtained a separation from bed and board from his wife in 1663, after he discovered she was committing adultery, and he had also been granted a divorce by an ecclesiastical court and had Lady Roos' children declared illegitimate. In March 1670, Lord Roos asked Parliament to allow him to remarry. The debate on the Roos divorce bill became politically charged because it impacted on whether Parliament could legally allow Charles to remarry. During the debate, Ashley spoke out strongly in favour of the Roos divorce bill, arguing that marriage was a civil contract, not a sacrament. Parliament ultimately gave Lord Roos permission to remarry, but Charles II never attempted to divorce his wife.
