Responses

I think it said that only members of the royal family and the vampire race can see the paper is red. Even though he didnt know he was the 1st prince, he is still the first true heir to the kingdom. And because he has that blood, and people all still call'Alexei' the first prince, he is royal whether they know he is alive or not. So he would fall into the category of those who can the paper is red and also why he could destroy the contract.
Idk if this makes sense. Hopefully it clarified rather than confused.
Wait....so how was he able to see the red paper???? And he didn't reclaim his king status?