@Akera93 He's not weak because of hatred in general, but because the twins don't take pride in being part of the Imperial family. The other guardians are strong because the other princes take pride in being members of the Imperial family.
@Thoxi1026 I'd assume it has to do with key nobles not wanting the status quo to change by allowing others to move up the ranks. Allowing a 'no-one' and their family to become nobles would be the same as admitting that the nobles aren't as all-powerful and impressive as some of them would claim...