The Little Queen

Starlie Elmhurst was practically born into the royal family. Her parents, Lady Elizabeth and Lord Lucius made a deal with the King and Queen before her birth that she would be betrothed to the Crown Prince Theodore. The deal states that she is to be married whenever Theo takes the throne i.e. whenever the King dies. The deal their parents made with each other doesn't worry the two as the grow up and become close with each other anyways.

Things arent always all sunshine and rainbows though, and Starlie learns that the hard way. Theo grows up and becomes distant....

until one fatality brings them back together.