Okay, so I'm feeling a threesome.
My idea is that a princess is kidnapped by some kind of baddie, can be discussed. The king sends his best knight, a dragon rider, to rescue the princess. The dragon can be a shapeshifter. But to keep his ability secret, is human within the kingdom, but when the knight goes to him as a dragon, goes to the cave that the dragon "lives" in. It is there that he takes his dragon form.
The knight of course knows he is a shapeshifter and the man is his best friend and perhaps a lover?
No one in the kingdom has ever met or seen the princess really as the king wants to ensure her virtue so she'll marry the prince of the large kingdom across the sea and their kingdoms can unite.
But when they find her, they feel an unbelievable attraction to the princess and she to them. She won't understand the attraction to the dragon yet, until she see's him shift back to his human form.
This is the basic plotline. As to what happens, can be discussed with my partners. PM me if interested. And PM only please. I'd like to keep this thread clean.