Help!

Anybody know anything about titles? Like King, Queen, Duke , that sort of title. Here's the story. My first book, (see below) there's an Empress. Now that I'm writing the sequel, well, everyone's life has changed a little. The Empress has married.. she married a Duke. I want to call him Prince Consort, but I'm not sure that's the right title, like if she was just a Queen. They had a daughter - is she a princess??

Anybody who knows the answer, I will be most grateful for your help. (Maybe Medievalist?)

Thank you I like that - Imperial Consort. Imperial Princess sounds a bit much though - she's only a baby. Maybe I'll use it once, just when I introduce the character, then cut it down to just Princess.

Thank UJ I know a bit about heraldry (I can draw a device and even put the right colors together) but titles go right over my head LOL.