If you want your characters to have king and queen like speaking style, then you can use plural verb instead of single. For example, a dialogue can be: "We like this crockery." Also, try to include old words and old speaking styles. For example, instead of "I want this book", write "We wish this book to be a part of our collection." You can research the medieval English words. Do not use too difficult ones of them, that are difficult to identify today, just use the words that sound old and that don't need a dictionary.