Duke. of Suffolk (Charles Brandon Duke of Suffolk). Henry's closest friend, he married Mary, the King's sister. The King banished him from court for a period after this, as Brandon did not seek his permission to marry Mary. However, he was eventually reinstated at court and was married to Mary, producing 4 children, until her death from Tuberculosis.
I love how mouthy Merlin is to Arthur. Or, to everyone in general. :) Even though Arthur is the prince and could have merlin punished for his witty quips, Arthur just takes it because he knows that merlin is really his closest friend.