1) Benjamin Valois: Obviously the main character. At the start of the book he's a newborn. Next age we see is 10, then 12, and at the most critical point of the book he's 15. At the end of this book he's 16. Blonde, a perfect brother.
2) Markus Valois: The antagonist. AKA the older brother and Crown Prince. At the very beginning he's 5. Then 15, 17, 20, and 21. He absolutely hates Benjamin. With a passion. That's a really bad thing.
3 + 4) Annamarie and Eloise Valois: Twins right under Markus in age. Therefore: At the very beginning 4. then 14, 16, 19, and 20. Almost completely identical. Annemarie's older by a few minutes. She has brown hair. Eloise has red hair, but definitely not the temper, except in more extreme cases. They both believe Benjamin
5) Elanore Valois: The mother of all of the above mentioned people. Believes Benjamin and the twins.
6) Henry Valois: The father and King of Avening. Does not believe Benjamin at the beginning.
Only a few people in the beginning who are major characters. There are a few minor ones: a few guards, a couple friends of Markus, etc. :) This will be fun.