2nd prince was ill when he was a child I guess.. 1st prince is the official prince. so he can't marry odette. but as 2nd prince is not that important, whoever he marries doesn’t matter.
i didn’t read the original story. so i maybe wrong though ╮( ̄▽ ̄)╭
Wait i dont understand how the other brother was able to marry to that guy but the other brother was locked up for that...I fail to understand ヽ(`Д´)ノ